RPG III – The Basics

Introduction – What is RPG III?

RPG III is a programming language created by IBM for business applications. It was designed to make it easy to create reports and process data on IBM midrange computers (AS/400 and IBM i systems).

Think of it like this: If modern languages like Python are like writing on a blank piece of paper where you can write anywhere, RPG III is like filling out a form where each piece of information has a specific box it must go in.

Why Learn RPG III?

Many large companies still run their core business systems on RPG III programs. These programs handle payroll, inventory, accounting, and more. Learning RPG III opens doors to well-paying jobs maintaining these critical systems.

Key Characteristics of RPG III

• Fixed Format: Code must be in exact column positions (like an old punch card)
• Business Focused: Designed for reports, file processing, and calculations
• Indicator Based: Uses numbered switches (01-99) to control program flow
• File Oriented: Built specifically to read and write database files

Lesson 1: Understanding the Fixed Format

The most important thing to understand about RPG III is that POSITION MATTERS. Every line of code has specific columns where different parts must go.

Think of it Like a Form

Imagine filling out a paper form where:

• Your name must go in columns 1-20
• Your city must go in columns 21-40
• Your zip code must go in columns 41-45

If you write your zip code in columns 1-5, the form won’t work. RPG III is exactly like this.

Step 1: Understanding the Basic Line Structure

Every RPG III line is divided into columns (positions):

Columns 1-5:   Sequence number (optional - usually left blank)
Column 6:      Form Type (tells what kind of line this is)
Columns 7-80:  The actual code (varies by form type)

The Six Form Types (Column 6)

Column 6 tells the computer what type of line this is:

Column 6	Name	Purpose	Simple Explanation
H	Header	Program settings	Like the title page of your program
F	File	Define files	Lists what files your program will use
E	Extension	Arrays and tables	Lists of related data
I	Input	Input record layout	Describes what data looks like coming in
C	Calculation	Program logic	Where you write your actual code
O	Output	Output formatting	How to format data going out

Example: Simple Program Structure

H
F* This is the File section - defines CUSTFILE
FCUSTFILE  IP   E           DISK
C* This is the Calculation section - the actual program
C                     READ  CUSTFILE               99
C                     SETON                        LR

Line by line explanation:

• Line 1 (H): Header – just an H in column 6
• Line 2 (F*): Comment line (asterisk means ignore this)
• Line 3 (F): Defines a file named CUSTFILE
• Line 4 (C*): Another comment
• Line 5 (C): Read a record from CUSTFILE
• Line 6 (C): Turn on the “Last Record” indicator

⚠️ Common Beginner Mistake:

Putting code in the wrong columns! If you put an F in column 5 instead of column 6, your program won’t compile. Always double-check your column positions.

Lesson 2: Your First RPG III Program

Let’s write the simplest possible RPG III program step by step. This program will:

1. Start
2. Print “Hello World”
3. End

Step 1: Create the Header Specification (H-Spec)

H

What this does: Tells the computer “this is an RPG III program.” The H must be in column 6.

Step 2: Define the Output File (F-Spec)

FQPRINT    O    F  132        PRINTER

Breaking this down:

• F in column 6 = File specification
• QPRINT (columns 7-14) = File name (system printer)
• O (column 15) = Output file
• F (column 16) = Full procedural (we control it)
• 132 (columns 20-23) = Line is 132 characters wide
• PRINTER (columns 36-42) = This is a printer file

Step 3: Write the Program Logic (C-Specs)

C                     EXCPT HELLO
C                     SETON                        LR

What each line does:

• Line 1: EXCPT HELLO = Print the line named “HELLO”
• Line 2: SETON LR = Turn on Last Record indicator (end program)

Step 4: Define the Output (O-Specs)

OQPRINT    E         HELLO
O                                   25 'Hello World!'

What this does:

• Line 1: Names this output line “HELLO”
• Line 2: Print “Hello World!” ending at column 25

Complete Program:

H
F* Define printer file
FQPRINT    O    F  132        PRINTER
C* Program logic
C                     EXCPT HELLO
C                     SETON                        LR
O* Output specification
OQPRINT    E         HELLO
O                                   25 'Hello World!'

💡 Understanding the Flow:

1. Program starts
2. EXCPT HELLO says “print the HELLO line”
3. Computer looks at O-specs and finds HELLO
4. Prints “Hello World!” at position 25
5. SETON LR ends the program

Lesson 3: Working with Files

Most RPG III programs work with database files. Let’s learn how to define a file step by step.

Understanding File Types

Files can be used in different ways:

• Input (I): Only reading data
• Output (O): Only writing new data
• Update (U): Reading AND changing data

Step 1: Simple Input File

FCUSTFILE  IP   E           DISK

Position by position:

• F (column 6) = File spec
• CUSTFILE (columns 7-14) = File name
• I (column 15) = Input file
• P (column 16) = Primary file
• E (column 19) = Externally described
• DISK (columns 20-27) = Disk file

What Does “Externally Described” Mean?

Simple explanation: The file structure (field names, sizes, types) is defined outside your program in the database. Your program just uses it.

Think of it like: You’re using a pre-printed form where all the boxes are already labeled. You don’t have to describe where each box is – you just fill them in.

Example: Defining Multiple Files

H
F* Input file - customer master
FCUSTFILE  IP   E           DISK
F* Output file - report
FREPORT    O    F  132        PRINTER
F* Update file - transaction file
FTRANSFILE UF   E           DISK

This program uses:

• CUSTFILE – reads customer records
• REPORT – prints output
• TRANSFILE – reads and updates transactions

⚠️ Remember:

The P in position 16 (Primary) is special – this file “drives” your program. The program will automatically read this file record by record.

Lesson 4: Calculations and Math

Now let’s learn how to do calculations. In RPG III, calculations are done on C-specs (C in column 6).

The Calculation Line Structure

C     Factor1   Operation   Factor2   Result   Length

Think of it as: Factor1 OperationName Factor2 = Result

Example 1: Simple Addition

Goal: Add 100 + 50

C           AMOUNT    ADD   50          AMOUNT    72

Breaking it down:

• C (column 6) = Calculation spec
• AMOUNT (columns 9-17) = Factor 1 (first number)
• ADD (columns 18-27) = Operation (add them)
• 50 (columns 28-32) = Factor 2 (second number)
• AMOUNT (columns 33-42) = Result (where answer goes)
• 72 (columns 43-48) = Length (7 digits, 2 decimals)

What happens: Takes AMOUNT, adds 50, puts result back in AMOUNT

Example 2: Multiplication

Goal: Multiply QTY × PRICE

C           QTY       MULT  PRICE       TOTAL     92

What happens: QTY × PRICE = TOTAL (9 digits, 2 decimals)

Common Math Operations

Operation	What It Does	Example
ADD	Addition	100 + 50 = 150
SUB	Subtraction	100 – 30 = 70
MULT	Multiplication	5 × 10 = 50
DIV	Division	100 ÷ 4 = 25
Z-ADD	Set to zero then add	Set TOTAL to 0

Complete Calculation Example

Calculate: Sales tax on an item

C* Price = 100.00
C                     Z-ADD 100.00      PRICE     92
C* Tax rate = 0.08 (8%)
C                     Z-ADD 0.08        TAXRATE   32
C* Calculate tax
C           PRICE     MULT  TAXRATE     TAX       92
C* Calculate total
C           PRICE     ADD   TAX         TOTAL     92

Step by step:

1. Set PRICE = 100.00
2. Set TAXRATE = 0.08
3. Calculate TAX = 100.00 × 0.08 = 8.00
4. Calculate TOTAL = 100.00 + 8.00 = 108.00

💡 Understanding Field Lengths:

The numbers at the end (like 92, 72) tell the size:

• 92 = 9 digits total, 2 after decimal (1234567.89)
• 72 = 7 digits total, 2 after decimal (12345.67)
• 50 = 5 digits, no decimals (12345)

Lesson 5: Making Decisions (IF Statements)

Programs need to make decisions. “IF the customer owes money, THEN send a bill.”

Simple IF Statement

Example: Check if balance is over $1000

C           BALANCE   IFGT  1000
C                     EXSR  HIGHBAL
C                     ENDIF

What this means in English:

• IF BALANCE is Greater Than 1000
• THEN Execute Subroutine HIGHBAL
• END of IF statement

IF Operations

Operation	Meaning	Example
IFEQ	IF Equal	If STATUS equals ‘A’
IFNE	IF Not Equal	If CODE not equal ‘X’
IFGT	IF Greater Than	If AMOUNT greater than 100
IFLT	IF Less Than	If AGE less than 21
IFGE	IF Greater or Equal	If SCORE ≥ 90
IFLE	IF Less or Equal	If QTY ≤ 10

Example: Simple Discount Calculator

C* If amount over $100, give 10% discount
C           AMOUNT    IFGT  100
C           AMOUNT    MULT  0.10        DISC      92
C                     ELSE
C* Otherwise, no discount
C                     Z-ADD 0           DISC      92
C                     ENDIF
C* Calculate final price
C           AMOUNT    SUB   DISC        FINAL     92

In plain English:

1. IF amount is over $100
2. THEN discount = amount × 10%
3. ELSE discount = 0
4. Final price = amount – discount

Multiple Conditions (AND)

Example: Check two things at once

C           AMOUNT    IFGT  1000
C           STATUS    ANDEQ 'A'
C                     EXSR  PROCESS
C                     ENDIF

What this means:

• IF AMOUNT > 1000 AND STATUS = ‘A’
• THEN run PROCESS subroutine
• Both conditions must be true

Real-World Example: Credit Approval

C* Check if customer qualifies for credit
C           CREDIT    IFGE  5000
C           RATING    ANDEQ 'GOOD'
C           LATE      ANDLE 2
C* Approved!
C                     MOVEL 'APPROVED' STATUS    20
C                     ELSE
C* Denied
C                     MOVEL 'DENIED'   STATUS    20
C                     ENDIF

Explanation:

Customer is approved IF:

• Credit limit ≥ $5000 AND
• Rating = ‘GOOD’ AND
• Late payments ≤ 2

If all three are true, STATUS = ‘APPROVED’, else ‘DENIED’

Lesson 6: Loops and Repetition

Loops let you repeat code multiple times. Like saying “Do this 10 times” or “Keep doing this until you’re done.”

The DOW Loop (Do While)

Simple idea: Keep doing something WHILE a condition is true.

Example: Count from 1 to 10

C* Start at 1
C                     Z-ADD 1           COUNT     30
C* Loop while COUNT is less than or equal to 10
C           COUNT     DOWLE 10
C* Print the number
C                     EXCPT DETAIL
C* Add 1 to COUNT
C           COUNT     ADD   1           COUNT
C                     ENDDO

What happens:

1. Set COUNT = 1
2. Is COUNT ≤ 10? Yes, so continue
3. Print COUNT
4. Add 1 to COUNT (now it’s 2)
5. Go back to step 2
6. Repeat until COUNT = 11, then stop

Loop Types

Operation	Meaning	When to Use
DOWLE	Do While Less or Equal	Repeat while value ≤ something
DOWLT	Do While Less Than	Repeat while value < something
DOWGT	Do While Greater Than	Repeat while value > something
DOWEQ	Do While Equal	Repeat while value = something
DOWNE	Do While Not Equal	Repeat while value ≠ something

Practical Example: Calculate Total Sales

C* Initialize total to zero
C                     Z-ADD 0           TOTAL     92
C* Read first record
C                     READ  SALESFILE             99
C* Loop until end of file (indicator 99 = end)
C  N99                DOW   *IN99 = *OFF
C* Add this sale to total
C           TOTAL     ADD   SALE        TOTAL
C* Read next record
C                     READ  SALESFILE             99
C                     ENDDO
C* Print the total
C                     EXCPT TOTLINE

Step by step:

1. Set TOTAL = 0
2. Read first record
3. If not end of file (N99 = NOT indicator 99):
4. Add SALE to TOTAL
5. Read next record
6. Repeat step 3
7. When end of file, print TOTAL

💡 Understanding *IN99:

*IN99 is an indicator. Think of it as a light switch:

• *OFF = switch is off = more records to read
• *ON = switch is on = end of file reached

N99 means “NOT 99” – so “keep going while NOT at end of file”

Simple Fixed Loop

Example: Do something exactly 5 times

C                     Z-ADD 1           X         30
C           X         DO    5
C                     EXSR  PROCESS
C           X         ADD   1           X
C                     ENDDO

What happens: Runs PROCESS subroutine 5 times

Lesson 7: Indicators Explained Simply

Indicators are like light switches in your program. They can be ON or OFF, and you use them to remember things and control what happens.

What Are Indicators?

Simple analogy: Imagine you have 99 sticky notes on your desk, numbered 01 to 99. You can:

• Flip a note face-up (turn indicator ON)
• Flip it face-down (turn indicator OFF)
• Check if it’s face-up or face-down (test the indicator)

How to Use Indicators

Step 1: Turning Indicators ON

C                     SETON                    25

What this does: Turns ON indicator 25 (like flipping sticky note #25 face-up)

Step 2: Turning Indicators OFF

C                     SETOF                    25

What this does: Turns OFF indicator 25 (flips it face-down)

Step 3: Using Indicators in Conditions

C  25                 EXSR  ERROR

What this means: “IF indicator 25 is ON, THEN run ERROR subroutine”

The 25 in columns 7-8 means “only do this line if 25 is ON”

Step 4: NOT Indicators

C  N25                EXSR  GOOD

What this means: “IF indicator 25 is OFF, THEN run GOOD subroutine”

The N means NOT – do this if 25 is NOT on

Practical Example: Error Checking

C* Turn off error indicator
C                     SETOF                    90
C* Check if amount is valid
C           AMOUNT    IFLE  0
C* Bad amount - turn on error indicator
C                     SETON                    90
C                     ENDIF
C* Check if status is valid
C           STATUS    IFNE  'A'
C           STATUS    ANDNE 'I'
C* Bad status - turn on error indicator
C                     SETON                    90
C                     ENDIF
C* If no errors, process the record
C  N90                EXSR  PROCESS
C* If errors, print error message
C  90                 EXCPT ERRLINE

How it works:

1. Start with error indicator OFF
2. Check if AMOUNT ≤ 0 (bad) → turn error ON
3. Check if STATUS isn’t ‘A’ or ‘I’ (bad) → turn error ON
4. If indicator 90 is OFF (no errors) → process
5. If indicator 90 is ON (has errors) → print error

Special Indicators

Indicator	Name	Purpose
LR	Last Record	Turns ON to end the program
99	End of File	Commonly used for EOF (no more records)
01-98	General Purpose	You can use these for anything you want
OF	Overflow	Turns ON when printer page is full

💡 Best Practice:

Give your indicators meaningful purposes and document them:

C* Indicator usage:
C* 90 = Error detected
C* 25 = High balance customer
C* 50 = Weekend transaction
C* 99 = End of file

Lesson 8: Reading and Writing Files

Now let’s learn how to actually work with database files – reading records, finding specific records, and updating them.

Reading Files Sequentially (READ)

Sequential means reading records in order, one after another, like reading a book page by page.

Basic READ Pattern

C* Read the first record
C                     READ  CUSTFILE               99
C* Loop until end of file
C  N99                DOW   *IN99 = *OFF
C* Process this record
C                     EXSR  PROCESS
C* Read the next record
C                     READ  CUSTFILE               99
C                     ENDDO

How it works:

1. READ gets one record from CUSTFILE
2. If successful, indicator 99 stays OFF
3. If no more records, indicator 99 turns ON
4. N99 means “while NOT at end of file”

Random Access (CHAIN)

Random access means finding a specific record directly, like looking up a phone number in a directory.

Basic CHAIN Pattern

C* Look for customer number 12345
C                     Z-ADD 12345       CUSTNO    50
C* Find this customer
C           CUSTNO    CHAIN CUSTFILE               95
C* If found (indicator 95 is OFF)
C  N95                EXSR  PROCESS
C* If not found (indicator 95 is ON)
C  95                 EXSR  NOTFOUND

How it works:

• CHAIN looks for a record with key = CUSTNO
• If found: indicator 95 stays OFF, record data is available
• If not found: indicator 95 turns ON

Writing New Records (WRITE)

Adding a New Customer

C* Set up the new customer data
C                     Z-ADD 99999       CUSTNO    50
C                     MOVEL 'John Smith'CUSTNAME  30
C                     Z-ADD 0           BALANCE   92
C* Write the new record
C                     WRITE CUSTREC

What happens: Creates a new record in the file with this data

Updating Existing Records (UPDATE)

Changing a Customer’s Balance

C* Find the customer
C           CUSTNO    CHAIN CUSTFILE               95
C  N95                EXSR  DOUPDATE
C  95                 EXSR  NOTFOUND
C
C* Update subroutine
C           DOUPDATE  BEGSR
C* Add to the balance
C           BALANCE   ADD   100.00      BALANCE
C* Save the changes
C                     UPDATE CUSTREC
C                     ENDSR

Important: You must CHAIN or READ before you UPDATE

Deleting Records (DELETE)

Removing a Customer

C* Find the customer
C           CUSTNO    CHAIN CUSTFILE               95
C* If found, delete it
C  N95                DELETE CUSTREC

Warning: DELETE permanently removes the record!

Complete File Processing Example

H
F* Files
FCUSTFILE  UF   E           DISK
FREPORT    O    F  132        PRINTER
C* Process all customers
C                     READ  CUSTFILE               99
C  N99                DOW   *IN99 = *OFF
C* If balance over 1000, add 5% interest
C           BALANCE   IFGT  1000
C           BALANCE   MULT  1.05        BALANCE
C                     UPDATE CUSTREC
C                     ENDIF
C* Print this customer
C                     EXCPT DETAIL
C* Read next customer
C                     READ  CUSTFILE               99
C                     ENDDO
C* End program
C                     SETON                        LR
O* Output
OREPORT    E         DETAIL
O                    CUSTNO        10
O                    CUSTNAME      40
O                    BALANCE  1    55

What this program does:

1. Read each customer record
2. If balance > $1000, add 5% interest
3. Save the updated balance
4. Print customer information
5. Repeat until all customers processed

⚠️ File Operation Rules:

• READ: Gets next record in sequence
• CHAIN: Finds specific record by key
• WRITE: Adds new record (can’t already exist)
• UPDATE: Must READ or CHAIN first
• DELETE: Must READ or CHAIN first

Lesson 9: Complete Program Example

Now let’s put everything together into a complete, working program. This program will:

1. Read a customer file
2. Calculate 5% commission on sales
3. Print a report showing each customer
4. Print totals at the end

Complete Commission Report Program

H* =============================================
H* COMMISSION REPORT PROGRAM
H* Calculates 5% commission on customer sales
H* =============================================
H
F* ============================================
F* FILE DEFINITIONS
F* ============================================
F* Customer file - input
FCUSTFILE  IP   E           DISK
F* Report - output
FREPORT    O    F  132        PRINTER
F
C* ============================================
C* MAIN PROGRAM
C* ============================================
C
C* Initialize totals
C                     EXSR  INIT
C
C* Process all customers
C                     READ  CUSTFILE               99
C  N99                DOW   *IN99 = *OFF
C                     EXSR  PROCESS
C                     READ  CUSTFILE               99
C                     ENDDO
C
C* Print final totals
C                     EXSR  TOTALS
C
C* End program
C                     SETON                        LR
C
C* ============================================
C* SUBROUTINES
C* ============================================
C
C* Initialize subroutine
C           INIT      BEGSR
C* Set all totals to zero
C                     Z-ADD 0           TOTSALES  102
C                     Z-ADD 0           TOTCOMM   92
C                     Z-ADD 0           CUSTCNT   50
C* Print report header
C                     EXCPT HEADER
C                     ENDSR
C
C* Process one customer
C           PROCESS   BEGSR
C* Calculate 5% commission
C           SALES     MULT  0.05        COMM      92
C* Add to totals
C           TOTSALES  ADD   SALES       TOTSALES
C           TOTCOMM   ADD   COMM        TOTCOMM
C           CUSTCNT   ADD   1           CUSTCNT
C* Print detail line
C                     EXCPT DETAIL
C                     ENDSR
C
C* Print totals
C           TOTALS    BEGSR
C* Calculate average commission
C           TOTCOMM   DIV   CUSTCNT     AVGCOMM   92
C* Print total lines
C                     EXCPT TOTLINE
C                     ENDSR
C
O* ============================================
O* OUTPUT SPECIFICATIONS
O* ============================================
O
O* Report header
OREPORT    E         HEADER    2
O                                   50 'SALES COMMISSION'
O                                   65 'REPORT'
O          E         HEADER    2
O                                   15 'CUSTOMER'
O                                   35 'CUSTOMER NAME'
O                                   55 'SALES'
O                                   75 'COMMISSION'
O          E         HEADER    1
O                                   75 '----------'
O
O* Detail line (one per customer)
O          E         DETAIL    1
O                    CUSTNO        15
O                    CUSTNAME      35
O                    SALES    1    55
O                    COMM     1    75
O
O* Total lines
O          E         TOTLINE   2
O                                   40 'TOTAL CUSTOMERS:'
O                    CUSTCNT  Z    55
O          E         TOTLINE   1
O                                   40 'TOTAL SALES:'
O                    TOTSALES 1    55
O          E         TOTLINE   1
O                                   40 'TOTAL COMMISSION:'
O                    TOTCOMM  1    75
O          E         TOTLINE   1
O                                   40 'AVERAGE COMMISSION:'
O                    AVGCOMM  1    75

Program Flow Explained

Step 1: Initialization (INIT subroutine)

1. Set TOTSALES = 0
2. Set TOTCOMM = 0
3. Set CUSTCNT = 0
4. Print report headers

Step 2: Main Loop

1. Read first customer record
2. If not end of file:
3.   • Run PROCESS subroutine
4.   • Read next customer
5.   • Go back to step 2
6. When end of file, continue to step 3

Step 3: Processing (PROCESS subroutine)

1. Calculate COMM = SALES × 0.05
2. Add SALES to TOTSALES
3. Add COMM to TOTCOMM
4. Add 1 to CUSTCNT
5. Print customer detail line

Step 4: Totals (TOTALS subroutine)

1. Calculate AVGCOMM = TOTCOMM ÷ CUSTCNT
2. Print all total lines

💡 Understanding the Output:

The report will look like this:

           SALES COMMISSION REPORT

CUSTOMER      CUSTOMER NAME        SALES    COMMISSION
                                           ----------
12345         John Smith          5000.00      250.00
12346         Jane Doe            7500.00      375.00
12347         Bob Johnson         3200.00      160.00

TOTAL CUSTOMERS:                         3
TOTAL SALES:                      15700.00
TOTAL COMMISSION:                           785.00
AVERAGE COMMISSION:                         261.67

Lesson 10: Practice Exercises

Now it’s time to practice! Try these exercises to test your understanding.

Exercise 1: Simple Calculator (Beginner)

Goal: Create a program that:

1. Sets NUM1 = 100
2. Sets NUM2 = 50
3. Calculates SUM = NUM1 + NUM2
4. Calculates DIFF = NUM1 – NUM2
5. Calculates PROD = NUM1 × NUM2
6. Prints all results

Hint: Use Z-ADD to set values, then ADD, SUB, MULT operations

Exercise 2: Grade Calculator (Intermediate)

Goal: Read a student file and assign letter grades:

• 90-100: Grade = ‘A’
• 80-89: Grade = ‘B’
• 70-79: Grade = ‘C’
• 60-69: Grade = ‘D’
• Below 60: Grade = ‘F’

Hint: Use IFGE (if greater or equal) operations

C           SCORE     IFGE  90
C                     MOVEL 'A'         GRADE      1
C                     ELSE
C           SCORE     IFGE  80
C                     MOVEL 'B'         GRADE      1
C                     ELSE
C* ... continue for C, D, F
C                     ENDIF
C                     ENDIF

Exercise 3: Inventory Reorder (Advanced)

Goal: Create a program that:

1. Reads an inventory file
2. Checks if quantity on hand < reorder point
3. If yes, calculates order quantity = (max quantity – current quantity)
4. Prints reorder report showing items to reorder
5. Counts total items needing reorder
6. Calculates total order value (quantity × cost)

Sample solution structure:

C* Initialize
C                     Z-ADD 0           ORDTOT    92
C                     Z-ADD 0           ORDCNT    30
C
C* Process each item
C                     READ  INVFILE                99
C  N99                DOW   *IN99 = *OFF
C
C* Check if reorder needed
C           ONHAND    IFLT  REORDER
C
C* Calculate order quantity
C           MAXQTY    SUB   ONHAND      ORDERQTY  50
C
C* Calculate order cost
C           ORDERQTY  MULT  COST        ORDCOST   92
C
C* Update totals
C           ORDTOT    ADD   ORDCOST     ORDTOT
C           ORDCNT    ADD   1           ORDCNT
C
C* Print this item
C                     EXCPT DETAIL
C
C                     ENDIF
C
C* Read next item
C                     READ  INVFILE                99
C                     ENDDO
C
C* Print totals
C                     EXCPT TOTALS

💡 Practice Tips:

• Start with the file definitions (F-specs)
• Write the main logic in C-specs
• Add output formatting last (O-specs)
• Test with small amounts of data first
• Add comments to explain what each section does

What’s Next – Modern RPG

Congratulations! You’ve learned the basics of RPG III. Now let’s talk about what comes next.

The Evolution of RPG

RPG has evolved over the years:

• RPG III (1970s-1980s) – What you just learned
• RPG/400 (1988) – Added more features
• RPG IV (1994) – Major upgrade, still fixed format
• ILE RPG (1995-now) – Modern, free-format

What’s Different in Modern RPG?

Same Logic, Different Syntax

RPG III (what you learned):

C           BAL       IFGT  1000
C                     EXSR  HIGHBAL
C                     ENDIF

Modern RPG (free-format):

If Balance > 1000;
  Exsr HighBalance;
EndIf;

See the difference? Same logic, but no column positions needed!

Modern RPG Benefits

• No column positions – Write code anywhere on the line
• Longer names – Field names can be 4096 characters instead of 6
• Built-in functions – %EOF instead of indicator 99
• SQL integration – Write SQL queries directly in RPG
• Procedures – Better than subroutines

💡 Your Next Steps:

1. Practice RPG III: Master the basics with the exercises above
2. Learn RPG IV: Same concepts, updated syntax
3. Explore ILE RPG: Modern free-format programming
4. Study SQL: Learn to embed SQL in RPG
5. Understand DDS: Learn how to create externally described files

Career Opportunities

Learning RPG opens many doors:

• Maintenance Programmer: Keep existing systems running
• Modernization Specialist: Convert RPG III to modern RPG
• IBM i Developer: Create new applications on IBM i
• Business Analyst: Understand legacy systems to document them

⚠️ Important:

Even though RPG III is “old,” millions of lines of RPG III code are running critical business systems RIGHT NOW. Companies need people who understand this code. Your new skills are valuable!

Summary: What You’ve Learned

🎓 You Now Know:

1. Fixed Format: How column positions work in RPG III
2. Form Types: H, F, E, I, C, O specifications
3. File Operations: READ, CHAIN, WRITE, UPDATE, DELETE
4. Calculations: ADD, SUB, MULT, DIV, Z-ADD
5. Decisions: IF/ELSE/ENDIF statements
6. Loops: DOW/ENDDO for repetition
7. Indicators: Using switches to control program flow
8. Complete Programs: How all pieces fit together

Key Takeaways

• RPG III is column-sensitive – position matters!
• Programs flow from top to bottom (unless loops/IFs change it)
• Indicators are like switches – ON or OFF
• Most programs follow: Initialize → Process Loop → Totals → End
• Comments are your friend – document everything!

Practice Makes Perfect

The best way to learn RPG III is to write programs. Start simple:

1. Write a program that just prints “Hello”
2. Add calculations (add two numbers)
3. Add file reading (process a small file)
4. Add decisions (if amount > 100 do something)
5. Add loops (process all records)
6. Combine everything into complete programs

Keep this tutorial as a reference. Come back to it when you need to remember how something works. Good luck with your RPG programming journey!