GATE CS 2022 Q.44: Data Types, Operators and Control Flow

What is printed by the following ANSI C program?

#include<stdio.h>

int main(int argc, char *argv[]){
        char a = 'P';
        char b = 'x';
        char c = (a & b) + '*';
        char d = (a | b) - '-';
        char e = (a ^ b) + '+';
        printf("%c %c %c\n", c, d, e);
        return 0;
}

ASCII encoding for relevant characters is given below

ASCII encoding table: A=65, B=66, C=67, ..., Z=90; a=97, b=98, c=99, ..., z=122; *=42, +=43, -=45.

z K S

122 75 83

P x +

Official answer and solution

Official answer: A
From: Official GATE 2022 answer key

Solution

Compute bitwise AND, OR, and XOR operations on ASCII values and add/subtract character offsets.

Given ASCII values from the table:

'P' = 80 = $01010000_2$
'x' = 120 = $01111000_2$
'*' = 42
'-' = 45
'+' = 43

Evaluating each variable:

$c = (a \,\&\, b) + \text{'*'}$
$80 \,\&\, 120 = 01010000_2 \,\&\, 01111000_2 = 01010000_2 = 80$ $c = 80 + 42 = 122$
ASCII 122 is 'z'.
$d = (a \mid b) - \text{'-'}$
$80 \mid 120 = 01010000_2 \mid 01111000_2 = 01111000_2 = 120$ $d = 120 - 45 = 75$
ASCII 75 is 'K'.
$e = (a \oplus b) + \text{'+'}$
$80 \oplus 120 = 01010000_2 \oplus 01111000_2 = 00101000_2 = 40$ $e = 40 + 43 = 83$
ASCII 83 is 'S'.

printf("%c %c %c\n", c, d, e) prints z K S.

Final answer

Option (A)

Common trap

Printing the integer ASCII numbers instead of formatting them as characters using %c.

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2022 Computer Science and Information Technology (CS)
Question: 44 of 65
Section: Computer Science and Information Technology

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