By default a real number is treated as a
Answer: B
Correct answer: double
An unsuffixed floating constant such as 3.14 has type double, and so does the result of ordinary floating arithmetic. A constant is made float by an f suffix and long double by an L. This is why passing a float to a variadic function promotes it to double.
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Which is false ?
Answer: C
Correct answer: A variable must be declared and defined at the same time
The two can be separated, which is exactly what extern is for - the declaration makes the name usable and the definition, elsewhere, allocates the storage. The other three statements are all true, including that shadowing in an inner scope is permitted.
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When we mention the prototype of a function?
Answer: B
Correct answer: Declaring
A prototype declares the function - its name, return type and parameter types - so the compiler can check calls and convert arguments correctly. The definition is the body, written once. Calling requires the declaration to be visible, which is why prototypes go in headers.
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Is there any difference in the following declarations?
int myfun(int arr[]);
int myfun(arr[20]);
Answer: A
Correct answer: Yes
The first declares a parameter of pointer type, written as an unsized array, which is legal. The second gives a bare identifier and a size with no type at all, which is not a declaration and will not compile. A size in a parameter’s brackets is permitted but ignored - the parameter is a pointer either way.
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Which of the following declaration is not supported by C?
Answer: A
Correct answer: String str;
C has no String type; a string is an array of char terminated by a null, or a pointer to one. The other two declarations are perfectly valid: char *str is a pointer to char, and 3e2 is simply 300 written in exponential form.
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Which keyword is used to prevent any changes in the variable within a C program?
Answer: C
Correct answer: const
const tells the compiler the object is not to be modified through that name, and an attempt to assign to it is diagnosed. volatile is the opposite kind of promise - that the object may change by means the compiler cannot see - and mutable and immutable are not C keywords at all.
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A variable declared in a function can be used in main?
Answer: B
Correct answer: False
A variable declared inside a function has block scope and no linkage, so it does not exist as far as any other function is concerned. Declaring it static changes its lifetime but not its scope - it persists between calls while remaining invisible outside the function.
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Does this compile without error?
int main()
{
for (int k = 0; k < 10>
return 0;
}
Answer: C
Compilers implementing C90 does not allow this but compilers implementing C99 allow it.
Output:
$ cc pgm4.c
pgm4.c: In function ‘main’:
pgm4.c:4: error: ‘for’ loop initial declarations are only allowed in C99 mode
pgm4.c:4: note: use option -std=c99 or -std=gnu99 to compile your code
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Which of the following statements should be used to obtain a remainder after dividing 3.14 by 2.1 ?
Answer: C
Correct answer: rem = fmod(3.14, 2.1);
The % operator requires integer operands, so it will not compile here. fmod is the floating point remainder function declared in math.h, and it is the only one of the four options that computes what the question asks for.
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Which of the following special symbol allowed in a variable name?
Answer: D
Correct answer: _ (underscore)
An identifier may contain letters, digits and the underscore, and may not begin with a digit. The underscore is therefore the only special character permitted, and it is how multi-word names are written where the language will not accept a hyphen or a space.
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