Functions Questions and Answers

Q: Which of the following is an external variable? int func (int a) { int b; return b; } int main() { int c; func (c); } int d;

Correct answer: dd is declared at file scope, so it is the external variable - even though it appears at the end of the file, which merely limits how much of the file can see it. a is a parameter, and b and c are locals; all three are automatic.

Q: What will be the output? int main() { printf("%d", d++); } int d = 10;

Correct answer: Compile time errord is declared after main, so at the point of use it is not in scope. Under C99 and later an undeclared identifier is an error; older compilers would have assumed int and then found the later definition consistent, but the modern answer is a compile error.

Q: What will be the output? double var = 8; int main() { int var = 5; printf("%d", var); }

Correct answer: 5The local int var = 5; shadows the file-scope double var = 8; throughout main, so %d is matched with an int and prints 5. Shadowing is legal - the two are different objects in different scopes.

Q: What is the output of this C code? double i; int main() { printf("%g\n",i); return 0; }

Correct answer: 0.000000A file-scope double is zero-initialised, so it holds 0.0. %g chooses the shorter of the fixed and exponential forms, and for zero the answer is 0 either way.

Q: Which part of the program address space is p stored in the code given below? int *p = NULL; int main() { int i = 0; p = &i; return 0; }

Correct answer: Data segmentp is a file-scope variable with an explicit initialiser, so it goes in the data segment, which holds initialised statics and whose contents come from the executable file. (Strictly, a pointer initialised to NULL is all-zero and many toolchains put it in BSS after all; the distinction the question is drawing is between explicitly initialised and not.)

Q: Which part of the program address space is p stored in the code given below? int *p; int main() { int i = 0; p = &i; return 0; }

Correct answer: Bss segmentp is at file scope with no initialiser, so it belongs in BSS - the block reserved for zero-initialised statics. BSS occupies no space in the executable file: only its size is recorded, and the loader zeroes it, which is why an uninitialised global costs nothing on disk.

Q: Can variable i be accessed by functions in another source file? int i; int main() { printf("%d\n", i); }

Correct answer: trueA variable at file scope has external linkage by default, so another source file can reach it by declaring extern int i;. Adding static to the definition is what would prevent that.

Q: Property of external variable to be accessed by any source file is called by C90 standard as:

Correct answer: external linkageLinkage is the term for whether a name refers to the same object across translation units; scope is where a name is visible within one. A file-scope variable has external linkage - the same object however many files declare it.

Q: What is the output of this C code? int *i; int main() { if (i == NULL) printf("true\n"); return 0; }

Correct answer: truei is at file scope with no initialiser, so it is zero-initialised - and for a pointer that means the null pointer. The comparison with NULL therefore succeeds and true is printed.

Q: What is the output of this C code? static int x = 5; void main() { x = 9; { int x = 4; } printf("%d", x); }

Correct answer: 9x = 9; assigns to the file-scope static variable, and the inner block’s int x = 4; declares a different variable that vanishes at the closing brace. So the printf, back outside, shows 9.

81.

Which of the following is an external variable?

int func (int a)
    {
        int b;
        return b;
    }
    int main()
    {
        int c;
        func (c);
    }
    int d;

Answer: D

Correct answer: d

d is declared at file scope, so it is the external variable - even though it appears at the end of the file, which merely limits how much of the file can see it. a is a parameter, and b and c are locals; all three are automatic.

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82.

What will be the output?

int main()
    {
        printf("%d", d++);
    }
    int d = 10;

A.9
B.10
C.11
D.Compile time error

Answer: D

Correct answer: Compile time error

d is declared after main, so at the point of use it is not in scope. Under C99 and later an undeclared identifier is an error; older compilers would have assumed int and then found the later definition consistent, but the modern answer is a compile error.

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83.

What will be the output?

double var = 8;
    int main()
    {
        int var = 5;
        printf("%d", var);
    }

A.5
B.8
C.Compile time error due to wrong format identifier for double
D.Compile time error due to redeclaration of variable with same name

Answer: A

Correct answer: 5

The local int var = 5; shadows the file-scope double var = 8; throughout main, so %d is matched with an int and prints 5. Shadowing is legal - the two are different objects in different scopes.

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84.

What is the output of this C code?

double i;
    int main()
    {
       printf("%g\n",i);
       return 0;
    }

A.0.000000
B.Garbage value
C.Depends on the compiler

Answer: A

Correct answer: 0.000000

A file-scope double is zero-initialised, so it holds 0.0. %g chooses the shorter of the fixed and exponential forms, and for zero the answer is 0 either way.

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85.

Which part of the program address space is p stored in the code given below?

int *p = NULL;
    int main()
    {
        int i = 0;
        p = &i;
        return 0;
    }

A.Code/text segment
B.Data segment
C.Bss segment
D.Stack

Answer: B

Correct answer: Data segment

p is a file-scope variable with an explicit initialiser, so it goes in the data segment, which holds initialised statics and whose contents come from the executable file. (Strictly, a pointer initialised to NULL is all-zero and many toolchains put it in BSS after all; the distinction the question is drawing is between explicitly initialised and not.)

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86.

Which part of the program address space is p stored in the code given below?

int *p;
    int main()
    {
        int i = 0;
        p = &i;
        return 0;
    }

A.Code/text segment
B.Data segment
C.Bss segment
D.Stack

Answer: C

Correct answer: Bss segment

p is at file scope with no initialiser, so it belongs in BSS - the block reserved for zero-initialised statics. BSS occupies no space in the executable file: only its size is recorded, and the loader zeroes it, which is why an uninitialised global costs nothing on disk.

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87.

Can variable i be accessed by functions in another source file?

int i;
    int main()
    {
        printf("%d\n", i);
    }

A.false
B.Only if static keyword is used
C.Depends on the type of the variable
D.true

Answer: D

Correct answer: true

A variable at file scope has external linkage by default, so another source file can reach it by declaring extern int i;. Adding static to the definition is what would prevent that.

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88.

Property of external variable to be accessed by any source file is called by C90 standard as:

A.external linkage
B.external scope
C.global scope
D.global linkage

Answer: A

Correct answer: external linkage

Linkage is the term for whether a name refers to the same object across translation units; scope is where a name is visible within one. A file-scope variable has external linkage - the same object however many files declare it.

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89.

What is the output of this C code?

int *i;
    int main()
    {
        if (i == NULL)
            printf("true\n");
        return 0;
    }

A.true
B.true only if NULL value is 0
C.Compile time error
D.Nothing

Answer: A

Correct answer: true

i is at file scope with no initialiser, so it is zero-initialised - and for a pointer that means the null pointer. The comparison with NULL therefore succeeds and true is printed.

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90.

What is the output of this C code?

static int x = 5;
    void main()
    {
        x = 9;
        {
            int x = 4;
        }
        printf("%d", x);
    }

Answer: A

Correct answer: 9

x = 9; assigns to the file-scope static variable, and the inner block’s int x = 4; declares a different variable that vanishes at the closing brace. So the printf, back outside, shows 9.

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