Quick Summary
- Reserved words have special functions in BASIC programs
- Cannot be used as variable names or labels
- Always written in UPPERCASE in traditional BASIC
- Essential for controlling program flow and data handling
- Common in WAEC/NECO Computer Studies questions
What Are BASIC Keywords?
Think of BASIC keywords as the grammar rules of programming. Just as you cannot use a verb where a noun should be in English, you cannot misuse keywords in BASIC. These words tell the computer what action to perform.
When you write a BASIC program, the computer scans your code looking for these special words. For example, when it sees PRINT, it knows you want to display something on the screen. When it sees INPUT, it knows you want the user to type something.
Nigerian students often make mistakes by trying to name variables “INPUT” or “PRINT”. This causes errors because the computer gets confused between your variable and the keyword.
Categories of BASIC Keywords
1. Input/Output Keywords
PRINT – Displays text or values on screen
Example: PRINT “Welcome to WAEC exam”
INPUT – Accepts data from keyboard
Example: INPUT “Enter your JAMB score”; SCORE
READ/DATA – Reads values from DATA statements
Example: READ NAME$, AGE
2. Program Control Keywords
IF…THEN…ELSE – Makes decisions based on conditions
Example: IF MARK >= 50 THEN PRINT “Pass” ELSE PRINT “Fail”
FOR…NEXT – Creates loops that repeat a fixed number of times
Example: FOR I = 1 TO 10: PRINT I: NEXT I
WHILE…WEND – Repeats while condition is true
GOTO – Jumps to specific line number
GOSUB/RETURN – Calls and returns from subroutines
3. Variable Assignment Keywords
LET – Assigns values to variables (optional in modern BASIC)
Example: LET PRICE = 5000
DIM – Declares array dimensions
Example: DIM STUDENTS(30)
4. Program Structure Keywords
REM – Adds remarks/comments (ignored during execution)
Example: REM This calculates CGPA
END – Marks program termination
STOP – Pauses program execution
5. Logical/Relational Keywords
AND – Both conditions must be true
OR – At least one condition must be true
NOT – Reverses logical value
Complete List of Common BASIC Keywords
| Keyword | Category | Purpose | Example |
|---|---|---|---|
| I/O | Display output | PRINT “Hello” | |
| INPUT | I/O | Accept input | INPUT A |
| LET | Assignment | Assign value | LET X = 10 |
| IF-THEN | Control | Conditional | IF X > 5 THEN PRINT X |
| FOR-NEXT | Control | Loop | FOR I=1 TO 10 |
| GOTO | Control | Jump to line | GOTO 100 |
| GOSUB | Control | Call subroutine | GOSUB 500 |
| RETURN | Control | Exit subroutine | RETURN |
| READ | I/O | Read from DATA | READ NAME$ |
| DATA | I/O | Store values | DATA 10, 20, 30 |
| DIM | Declaration | Define array | DIM A(50) |
| REM | Documentation | Add comment | REM Calculate total |
| END | Control | End program | END |
| STOP | Control | Pause program | STOP |
| STEP | Control | Loop increment | STEP 2 |
| TO | Control | Loop limit | TO 100 |
| AND | Logical | Both true | IF A>5 AND B<10 |
| OR | Logical | Either true | IF X=1 OR Y=2 |
| NOT | Logical | Reverse logic | IF NOT (X>10) |
Why You Cannot Use Keywords as Variable Names
Many students try code like this:
LET PRINT = 100
This causes an error. The computer sees PRINT and expects you to display something, not store a value. Always use descriptive variable names instead:
- ✓ TOTAL_SCORE instead of TOTAL (TOTAL might be reserved)
- ✓ STUDENT_NAME$ instead of NAME$ (NAME might conflict)
- ✓ EXAM_GRADE instead of GRADE
Sample BASIC Program Using Multiple Keywords
10 REM Program to calculate average of three subjects 20 DIM SUBJECTS(3) 30 PRINT "Enter marks for three subjects" 40 FOR I = 1 TO 3 50 INPUT "Enter mark"; SUBJECTS(I) 60 NEXT I 70 LET TOTAL = 0 80 FOR I = 1 TO 3 90 LET TOTAL = TOTAL + SUBJECTS(I) 100 NEXT I 110 LET AVERAGE = TOTAL / 3 120 IF AVERAGE >= 50 THEN PRINT "Pass" ELSE PRINT "Fail" 130 END
This program uses: REM, DIM, PRINT, FOR-NEXT, INPUT, LET, IF-THEN-ELSE, END
Common WAEC Exam Mistakes
- Using keywords as variable names – “INPUT” or “DATA” as variables causes errors
- Wrong spelling – Writing “PRIN” instead of “PRINT” or “INPT” instead of “INPUT”
- Mixing keywords – Using GOTO without line numbers, or FOR without NEXT
- Case sensitivity confusion – While traditional BASIC uses UPPERCASE, some versions accept lowercase
- Missing required pairs – FOR without NEXT, GOSUB without RETURN, IF without THEN
- Using = for comparison in IF statements without proper syntax
Practice Questions
Multiple Choice Questions
1. Which keyword is used to display output in BASIC?
a) SHOW
b) DISPLAY
c) PRINT ✓
d) OUTPUT
2. The keyword used to accept user input from keyboard is:
a) GET
b) INPUT ✓
c) READ
d) ACCEPT
3. Which pair of keywords must always be used together in BASIC?
a) PRINT and INPUT
b) FOR and NEXT ✓
c) LET and GOTO
d) READ and PRINT
4. The keyword REM is used to:
a) Remove variables
b) Add comments to programs ✓
c) Remember values
d) Repeat commands
Essay/Theory Questions
1. Explain what reserved words are in BASIC programming and state FOUR examples. (5 marks)
Tip: Define clearly, then list four keywords with their functions.
2. Write a BASIC program that uses at least SIX different keywords to calculate the sum of two numbers entered by the user. (8 marks)
Tip: Include REM, INPUT, LET, PRINT, END, and one logical operator if possible.
3. Distinguish between the following pairs of BASIC keywords: (6 marks)
(a) READ and INPUT
(b) GOTO and GOSUB
(c) END and STOP
Tip: Explain what each does and when to use each one.
Memory Aids
Input/Output keywords: P-I-R
PRINT – shows output
INPUT – gets input
READ – reads data
Loop keywords: F-W
FOR-NEXT – counted loops
WHILE-WEND – conditional loops
Control flow: I-G-G
IF-THEN – decisions
GOTO – jump to line
GOSUB – call subroutine
Related Topics
- BASIC programming language structure
- Variables and data types in BASIC
- Control structures in programming
- Loop statements (FOR-NEXT, WHILE-WEND)
- Logical and relational operators