GATE CS 2025 Set 2 — Question 19

MCQ+1 / -0.33MediumPointers & Pointer ArithmeticC ProgrammingProgramming & Data StructuresArrays & Strings in C

Programming & Data Structures → C Programming → Arrays & Strings in C

Last updated 5 September 2026

Question

Consider the following C program:#include <stdio.h> void stringcopy(char *, char *); int main() { char a[30] = "@#Hello World!"; stringcopy(a, a + 2); printf("%s\n", a); return 0; } void stringcopy(char *s, char *t) { while(*t) *s++ = *t++; } Which ONE of the following will be the output of the program?

Correct answer(D) Hello World!d!SolutionThe program defines a function stringcopy that copies characters from the source pointer t to the destination pointer s as long as *t is not the null terminator (\0).Inside main:1.char a[30] is initialized to "@#Hello World!".The array contents (indices 0-14) are: @, #, H, e, l, l, o, , W, o, r, l, d, !, \0.2. stringcopy(a, a + 2) is called.s points to a[0] ('@').t points to a[2] ('H').3. The while(*t) loop executes:It copies characters from t to s and increments both pointers.It copies the substring "Hello World!" (length 12) from indices 2-13 to indices 0-11.a[0] becomes 'H', a[1] becomes 'e', ..., a[11] becomes '!'.4. Crucially, the loop condition while(*t) checks the value before copying. When t reaches index 14 (the null terminator \0), the condition fails, and the loop terminates. The assignment *s++ = *t++ is NOT executed for the null terminator.5.Therefore, the null terminator is NOT copied to the new position (index 12). The character at index 12 remains what it was originally. Original a[12] was 'd'.Original a[13] was '!'.Original a[14] was \0.6. The final string in a is:Indices 0-11: Hello World!Index 12: d (unchanged)Index 13: ! (unchanged)Index 14: \0 (unchanged)Result: "Hello World!d!"7. printf("%s\n", a) prints the string up to the first null terminator.Output: Hello World!d!Turn this into a strength.Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer(D) Hello World!d!SolutionThe program defines a function stringcopy that copies characters from the source pointer t to the destination pointer s as long as *t is not the null terminator (\0).Inside main:1.char a[30] is initialized to "@#Hello World!".The array contents (indices 0-14) are: @, #, H, e, l, l, o, , W, o, r, l, d, !, \0.2. stringcopy(a, a + 2) is called.s points to a[0] ('@').t points to a[2] ('H').3. The while(*t) loop executes:It copies characters from t to s and increments both pointers.It copies the substring "Hello World!" (length 12) from indices 2-13 to indices 0-11.a[0] becomes 'H', a[1] becomes 'e', ..., a[11] becomes '!'.4. Crucially, the loop condition while(*t) checks the value before copying. When t reaches index 14 (the null terminator \0), the condition fails, and the loop terminates. The assignment *s++ = *t++ is NOT executed for the null terminator.5.Therefore, the null terminator is NOT copied to the new position (index 12). The character at index 12 remains what it was originally. Original a[12] was 'd'.Original a[13] was '!'.Original a[14] was \0.6. The final string in a is:Indices 0-11: Hello World!Index 12: d (unchanged)Index 13: ! (unchanged)Index 14: \0 (unchanged)Result: "Hello World!d!"7. printf("%s\n", a) prints the string up to the first null terminator.Output: Hello World!d!

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