What is the output of the following C program? #include int main() double a[2]=20.0, 25.0, *p, *q; p = a; q = p + 1; printf("%d,%d", (int)(q - p), (int)(*q - *p)); return 0; A) 4,8 B) 1,5 C) 8,5 D) 1,8

Official answer: B) 1,5. Explanation: Let us trace the given C program step-by-step: 1. Array and Pointer Initialization: - `a` is an array of two `double` elements: `a[0] = 20.0` and `a[1] = 25.0`. - `p` and `q` are pointers of type `double*`. - `p = a;` makes pointer `p` point to the first element `a[0]` (address `&a[0]`). - `q = p + 1;` performs pointer arithmetic, making pointer `q` point to the next `double` element `a[1]` (address `&a[1]`). 2. Evaluating `(int)(q - p)`: - In C, pointer subtraction (`q - p`) between two pointers of the same type yields the number of elements of that base type separating the two pointers, not the byte distance. - Since `q` points to `a[1]` and `p` points to `a[0]`, the pointer difference is `1`. - Casting to `int` gives `1`. 3. **Evaluating `(int)(*q - *p)`:** - Dereferencing `*q` gives `25.0` and `*p` gives `20.0`. - The arithmetic difference is 25.0 - 20.0 = 5.0. - Casting to `int` gives `5`. 4. Output: - The `printf` format string is `"%d,%d"`, which prints `1,5`. Hence, the correct option is (B).

Programming and Data Structures · Programming in C

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GATE CSE 2024 Set 2 Q36 · MCQ · 2 marks

What is the output of the following C program? `#include <stdio.h> int main() { double a[2]={20.0, 25.0}, p, q; p = a; q = p + 1; printf("%d,%d", (int)(q - p), (int)(q - p)); return 0; }`

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In GATE CS, Programming in C is tested extensively through rigorous code tracing, pointer mechanics, and fundamental semantics rather than high-level syntax trivia. Questions emphasize pointer arithmetic and multidimensional array decay, storage classes (especially static local variables), evaluation order, side effects of increment/decrement operators, parameter passing mechanisms (pass-by-value vs pass-by-reference), and recursive program state tracking. The topic features a nearly balanced split between NAT and MCQ items across 1-mark and 2-mark categories, demanding precise, bug-free execution traces without a compiler.

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Programming and Data Structures · Programming in C

Official IIT answer key · IISc Bangalore · Audited Aug 2026

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GATE CSE 2024 Set 2 Q36 · MCQ · 2 marks

What is the output of the following C program? `#include <stdio.h> int main() { double a[2]={20.0, 25.0}, p, q; p = a; q = p + 1; printf("%d,%d", (int)(q - p), (int)(q - p)); return 0; }`

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Programming in C

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Examiner trap & misconception

Topic notes

How GATE tests Programming in C

Full Programming in C guide →

More on Programming in C

All 74 questions on Programming in C →

Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.

What is the output of the following C program? `#include <stdio.h> int main() { double a[2]={20.0, 25.0}, p, q; p = a; q = p + 1; printf("%d,%d", (int)(q - p), (int)(q - p)); return 0; }`

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What is the output of the following C program? `#include <stdio.h> int main() { double a[2]={20.0, 25.0}, p, q; p = a; q = p + 1; printf("%d,%d", (int)(q - p), (int)(q - p)); return 0; }`

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What is the output of the following C program? #include <stdio.h> int main() { double a[2]={20.0, 25.0}, *p, *q; p = a; q = p + 1; printf("%d,%d", (int)(q - p), (int)(*q - *p)); return 0; }

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What is the output of the following C program? #include <stdio.h> int main() { double a[2]={20.0, 25.0}, *p, *q; p = a; q = p + 1; printf("%d,%d", (int)(q - p), (int)(*q - *p)); return 0; }

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What is the output of the following C program? `#include <stdio.h> int main() { double a[2]={20.0, 25.0}, p, q; p = a; q = p + 1; printf("%d,%d", (int)(q - p), (int)(q - p)); return 0; }`

What is the output of the following C program? `#include <stdio.h> int main() { double a[2]={20.0, 25.0}, p, q; p = a; q = p + 1; printf("%d,%d", (int)(q - p), (int)(q - p)); return 0; }`