Functions Questions and Answers

Q: What is the output of this C code? int x = 5; void main() { int x = 3; printf("%d", x); { x = 4; } printf("%d", x); }

Correct answer: 3 4The inner x = 4; is an assignment, not a declaration, so it changes the x already in scope - main's local. The first printf shows 3 and the second, after the block, shows 4. The file-scope x = 5 is shadowed throughout and never seen.

Q: Functions cannot return a floating point number

Correct answer: NoA function may return any type it likes, floating point included - double sqrt(double) is the obvious example. The statement is false.

Q: What is the output of this C code? double foo(); int main() { foo(); return 0; } foo() { printf("2 "); return 2; }

Correct answer: Compile time errorThe prototype declares double foo(), but the definition omits the return type and so defaults to int. The two conflict, and the compiler rejects the program.

Q: Names of functions in two different files linked together must be unique

Correct answer: TrueOnce two files are linked together they share a single global namespace, so two external functions with the same name collide and the linker reports a duplicate symbol. The way to avoid it is to declare a function static, which confines it to its own file.

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

Correct answer: 6 7A static local is initialised once, before the program starts, and keeps its value between calls - its storage lasts as long as the program even though its name is local. So the first call prints 6 and the second 7. An ordinary local would print 6 both times.

Q: What is the output of this C code? int foo(); int main() { int i = foo(); } foo() { printf("2 "); return 2; }

Correct answer: 2The prototype says int foo(), and the definition, which gives no return type, defaults to int - so the two agree. The program compiles and prints 2.

Q: What is the output of this C code? void main() { static int x = 3; x++; if (x <= 5) { printf("hi"); main(); } }

Correct answer: hi hix is static, so it is initialised to 3 once and keeps its value across the recursive calls. It becomes 4 on the first pass (prints hi), 5 on the second (prints hi), and 6 on the third, where the test fails and the recursion stops. So hi appears twice. Had x been ordinary, it would have been reset to 3 on every call and the recursion would never have ended.

Q: Which of the following function declarations is illegal?

Correct answer: None of the mentionedAll three are legal. Declaring a function before main and defining it afterwards is the normal pattern; a stray semicolon after a definition is an empty declaration, which is harmless; and a declaration inside a function is allowed, its scope being that block.

Q: The keyword used to transfer control from a function back to the calling function is

Correct answer: returnreturn ends the function and hands control - and optionally a value - back to the caller. goto can only jump within the same function, and there is no go back keyword.

91.

What is the output of this C code?

int x = 5;
    void main()
    {
        int x = 3;
        printf("%d", x);
        {
            x = 4;
        }
        printf("%d", x);
    }

A.Run time error
B.3 3
C.3 5
D.3 4

Answer: D

Correct answer: 3 4

The inner x = 4; is an assignment, not a declaration, so it changes the x already in scope - main's local. The first printf shows 3 and the second, after the block, shows 4. The file-scope x = 5 is shadowed throughout and never seen.

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92.

Functions cannot return a floating point number

A.Yes
B.No

Answer: B

Correct answer: No

A function may return any type it likes, floating point included - double sqrt(double) is the obvious example. The statement is false.

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93.

What is the output of this C code?

double foo();
    int main()
    {
        foo();
        return 0;
    }
    foo()
    {
        printf("2 ");
        return 2;
    }

A.2
B.Compile time error
C.Depends on the compiler
D.Depends on the standard

Answer: B

Correct answer: Compile time error

The prototype declares double foo(), but the definition omits the return type and so defaults to int. The two conflict, and the compiler rejects the program.

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94.

Names of functions in two different files linked together must be unique

A.True
B.False

Answer: A

Correct answer: True

Once two files are linked together they share a single global namespace, so two external functions with the same name collide and the linker reports a duplicate symbol. The way to avoid it is to declare a function static, which confines it to its own file.

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95.

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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96.

What is the output of this C code?

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

A.6 7
B.6 6
C.5 5
D.5 6

Answer: A

Correct answer: 6 7

A static local is initialised once, before the program starts, and keeps its value between calls - its storage lasts as long as the program even though its name is local. So the first call prints 6 and the second 7. An ordinary local would print 6 both times.

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97.

What is the output of this C code?

int foo();
    int main()
    {
        int i = foo();
    }
    foo()
    {
        printf("2 ");
        return 2;
    }

A.2
B.Compile time error
C.Depends on the compiler
D.Depends on the standard

Answer: A

Correct answer: 2

The prototype says int foo(), and the definition, which gives no return type, defaults to int - so the two agree. The program compiles and prints 2.

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98.

What is the output of this C code?

void main()
    {
        static int x = 3;
        x++;
        if (x <= 5)
        {
            printf("hi");
            main();
        }
    }

A.Run time error
B.hi
C.infinite hi
D.hi hi

Answer: D

Correct answer: hi hi

x is static, so it is initialised to 3 once and keeps its value across the recursive calls. It becomes 4 on the first pass (prints hi), 5 on the second (prints hi), and 6 on the third, where the test fails and the recursion stops. So hi appears twice. Had x been ordinary, it would have been reset to 3 on every call and the recursion would never have ended.

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99.

Which of the following function declarations is illegal?

A.double func(); int main(){} double func(){}
B.double func(){}; int main(){}
C.int main() { double func(); }double func(){//statements}
D.None of the mentioned

Answer: D

Correct answer: None of the mentioned

All three are legal. Declaring a function before main and defining it afterwards is the normal pattern; a stray semicolon after a definition is an empty declaration, which is harmless; and a declaration inside a function is allowed, its scope being that block.

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100.

The keyword used to transfer control from a function back to the calling function is

A.switch
B.goto
C.go back
D.return

Answer: D

Correct answer: return

return ends the function and hands control - and optionally a value - back to the caller. goto can only jump within the same function, and there is no go back keyword.

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