sqrt(x) function is not faster than the apparent equivalent pow(x,0.5).
Answer: B
Correct answer: false
sqrt(x) is faster - often much faster - than pow(x, 0.5). Square root is a single hardware instruction on most processors, whereas pow is a general routine computing an exponential and a logarithm. It is also more accurate, so sqrt should always be preferred.
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Point out the error in the following program.
#include <stdio.h>
int main()
{
char str[] = "IndiaBIX";
printf("%.#s %2s", str, str);
return 0;
}
Answer: D
Correct answer: No error
There is no error. %.#s and %2s are not the specifiers the author probably intended, but printf is not obliged to reject them - the format string is parsed at run time, and undefined or unrecognised conversions do not stop the program compiling. The array declaration is perfectly ordinary.
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What will be the output of the program?
#include <stdio.h>
#include <string.h>
int main()
{
char dest[] = {97, 97, 0};
char src[] = "aaa";
int i;
if((i = memcmp(dest, src, 2))==0)
printf("Got it");
else
printf("Missed");
return 0;
}
Answer: B
memcmp compares the first 2 bytes of the blocks dest and src as unsigned chars. So, the ASCII value of 97 is 'a'.
if((i = memcmp(dest, src, 2))==0) When comparing the array dest and src as unsigned chars, the first 2 bytes are same in both variables.so memcmp returns '0'.
Then, the if(0=0) condition is satisfied. Hence the output is "Got it".
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Point out the error in the following program.
#include <stdio.h>
int main()
{
fprintf("IndiaBIX");
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 is stderr?
Answer: C
Correct answer: standard error streams
stderr is one of the three standard streams opened automatically, alongside stdin and stdout. Error messages go to it rather than to stdout so that they still appear when the program’s output is redirected to a file - and because it is unbuffered, they appear at once.
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MB_CUR_MAX is not defined in stdlib.h.
Answer: B
Correct answer: false
MB_CUR_MAX is defined in <stdlib.h>. It gives the maximum number of bytes in a multibyte character for the current locale, and it is needed by the conversion functions such as mbtowc.
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Which standard library function will you use to find the last occurrence of a character in a string in C?
Answer: D
Correct answer: strrchr()
strrchr() - the extra r is for reverse - returns a pointer to the last occurrence of a character in a string, or NULL if it is absent. It is the usual way to find a file extension or the last separator in a path. The other three names do not exist; strchr() finds the first occurrence.
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What does the strcmp() function return when the two strings compared are identical ?
Answer: B
Correct answer: 0
strcmp() returns zero for identical strings, a negative value when the first sorts before the second and a positive value otherwise. The common mistake is to treat a zero return as false and so invert the test.
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Input/output function prototypes and macros are defined in which header file?
Answer: C
Correct answer: stdio.h
<stdio.h> declares the input and output functions - printf, scanf, fopen, fgets - and the macros and types they use, including FILE, EOF, NULL and the SEEK_ constants. conio.h and dos.h are non-standard DOS headers.
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Which header file must be included to use the printf() and scanf() functions ?
Answer: C
Correct answer: stdio.h
The standard input and output declarations, including printf and scanf, live in stdio.h. stdlib.h provides memory allocation and conversion routines, string.h the string handling functions and math.h the mathematical ones.
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