WBBSE Madhyamik Computer Application (Optional): Programming in a High-Level Language (C)

What the examiner tests

Reading and writing short C programs: declarations, expressions, conditions and loops, plus predicting output.

Core rules

• Every C program has main(), statements end with ;, and blocks are enclosed in { }. #include <stdio.h> is needed for printf/scanf.
• Data types: int (whole numbers), float, double, char (one character in single quotes). printf uses %d, %f, %c, %s; scanf needs & before each variable.
• Operators: arithmetic + - * / %; relational < > <= >= == !=; logical && || !; assignment =; increment/decrement ++ --. *, /, % bind tighter than + and -, which bind tighter than relational operators, which bind tighter than logical operators. Use brackets when unsure.
• / between two integers gives an integer quotient (7/2 = 3), and % works only on integers.
• Control: if, if–else, else if ladder, switch (with break and default), for, while, and do–while, which always runs at least once.

Worked example

int a = 7, b = 2;
float c = a / b;
printf("%.1f", c);

Output: 3.0. The division happens first in integer arithmetic, giving 3; only then is 3 converted to float. To get 3.5, write (float)a / b.

Traps

• if (a = 5) assigns instead of comparing; use ==.
• Omitting & in scanf("%d", n).
• Forgetting break in switch, so control falls through.
• Putting a semicolon after for(...) or if(...), which detaches the body.
• Assuming 5 / 2 is 2.5 in C.