What is the output of this C code?
int foo();
int main()
{
int i = foo();
}
foo()
{
printf("2 ");
return 2;
}
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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What is the output of this C code?
void main()
{
static int x = 3;
x++;
if (x <= 5)
{
printf("hi");
main();
}
}
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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Which of the following function declarations is illegal?
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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The keyword used to transfer control from a function back to the calling function is
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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What will be the output?
int main()
{
printf("%d", d++);
}
int d = 10;
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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The keyword used to transfer control from a function back to the calling function is
Answer: D
The keyword return is used to transfer control from a function back to the calling function.
Example:
#include
int add(int, int); /* Function prototype */
int main()
{
int a = 4, b = 3, c;
c = add(a, b);
printf("c = %d\n", c);
return 0;
}
int add(int a, int b)
{
/* returns the value and control back to main() function */
return (a+b);
}
Output: c = 7
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What is the output of this C code?
int x = 5;
void main()
{
int x = 3;
printf("%d", x);
{
int x = 4;
}
printf("%d", x);
}
Answer: A
Correct answer: 3 3
Here the inner int x = 4; is a declaration, so it creates a new variable that shadows the outer one for the length of the block and then disappears. main’s own x is untouched, and both printf calls show 3.
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What will happen after compiling and running following code?
main()
{
printf("%p", main);
}
Answer: C
Function names are just addresses (just like array names are addresses).
main() is also a function. So the address of function main will be printed. %p in printf specifies that the argument is an address. They will be printed as hexadecimal numbers.
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Functions in C are ALWAYS:
Answer: B
Correct answer: External
A function in C has external linkage by default: its name is visible to every other file linked with it. That is why two files cannot define functions of the same name, and why static is used to confine a function to its own file.
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What is the default return type if it is not specified in function definition?
Answer: B
Correct answer: int
Under the older rules an omitted return type defaults to int. C99 removed the implicit int, so a modern compiler warns or refuses - but the default, where it is honoured, is int.
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