Which library function converts a string to a double-precision floating point value ?
Answer: C
Correct answer: atof()
atof() parses a string into a double, atoi() into an int and atol() into a long. strtok() is unrelated, splitting a string into tokens on a set of delimiters.
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ftell() returns the current position of the pointer in a file stream.
Answer: A
Correct answer: True
ftell(fp) returns the current position as a long - the byte offset from the start for a binary file. Its usual companion is fseek: save a position with ftell, read on, and return to it later.
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Which of the following macros is not defined?
Answer: A
Correct answer: ULONG_MIN
There is no ULONG_MIN, and there could be no use for one: the minimum of an unsigned type is always 0, so the standard defines only the maxima for unsigned types. Signed types get both, hence LONG_MIN and LONG_MAX.
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What will be the output of the program?
#include <stdio.h>
int main()
{
int i;
char c;
for(i=1; i<=5; i++)
{
scanf("%c", &c); /* given input is 'b' */
ungetc(c, stdout);
printf("%c", c);
ungetc(c, stdin);
}
return 0;
}
Answer: C
The ungetc() function pushes the character c back onto the named input stream, which must be open for reading.
This character will be returned on the next call to getc or fread for that stream.
One character can be pushed back in all situations.
A second call to ungetc without a call to getc will force the previous character to be forgotten.
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Which statement is true regarding abs() and labs()?
Answer: A
Correct answer: The abs() function is similar to the labs() function, except that the argument and the returned value each of them have type long int
The two do the same thing for different types: abs takes and returns an int, and labs takes and returns a long int. (llabs was added for long long, and fabs handles floating point.)
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FILE is a structure suitably typedef'd in "stdio.h".
Answer: A
Correct answer: True
FILE is a structure type defined in <stdio.h>, holding the buffer, the position indicator and the state flags for a stream. Programs use it only through a FILE * and never look inside - its contents are the implementation’s business.
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Which of the given function differs from the statement’errno is not necessarily set on conversion error’?
Answer: D
Correct answer: strtod()
strtod is the one that does report errors: on overflow or underflow it sets errno to ERANGE, and it also returns a pointer to the first unconverted character. The ato family - atoi, atof, atol - simply return 0 on failure and set nothing, which is why the strto functions should be preferred.
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Point out the error in the following program.
#include <stdio.h>
int main()
{
fprintf("Compscibits");
printf("%.ef", 2.0);
return 0;
}
Answer: B
Correct answer: Error: in fprintf() statement
fprintf requires a stream as its first argument - fprintf(stdout, "..."). Called with only a string it is missing that argument, and the string is taken as the stream, which is a type error. Plain printf is the version that writes to stdout without being told.
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What will be the output of the program?
#include <stdio.h>
int main()
{
int i;
char c;
for(i=1; i<=5; i++)
{
scanf("%c", &c); /* given input is 'a' */
printf("%c", c);
ungetc(c, stdin);
}
return 0;
}
Answer: B
Correct answer: aaaaa
ungetc pushes the character back onto the input stream, so the next scanf reads the same character again. The loop therefore reads and prints the same a on all five passes, giving aaaaa. Only one character of pushback is guaranteed, which is all this needs.
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What will be the output of the program?
#include <stdio.h>
int main()
{
int i;
char c;
for(i=1; i<=5; i++)
{
scanf("%c", &c); /* given input is 'a' */
printf("%c", c);
ungetc(c, stdin);
}
return 0;
}
Answer: B
Correct answer: aaaaa
ungetc pushes the character back onto the input stream, so the next scanf reads the same character again. The loop therefore reads and prints the same a on all five passes, giving aaaaa. Only one character of pushback is guaranteed, which is all this needs.
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