______ macro must be called before using ______ and ________
Answer: B
Correct answer: va_start, va_end and va_arg
va_start must be called before either of the others: it initialises the va_list from the last named parameter. va_arg then fetches the arguments one at a time, and va_end tidies up before the function returns.
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What is the purpose of the fflush() function?
Answer: A
Correct answer: flushes all streams and specified streams
fflush(fp) writes out the buffer of one stream; fflush(NULL) flushes every output stream. It matters because output is buffered: without a flush, text may still be sitting in memory when a program crashes. (fflush on an input stream is undefined behaviour, despite being widely misused.)
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What is the purpose of fflush() function.
Answer: A
"fflush()" flush any buffered output associated with filename, which is either a file opened for writing or a shell command for redirecting output to a pipe or coprocess.
Example:
fflush(FilePointer);
fflush(NULL); flushes all streams.
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Which of the following library functions is used to read location dependent information?
Answer: B
Correct answer: localeconv()
localeconv() returns a pointer to a struct lconv describing the current locale’s numeric and monetary conventions - the decimal point, the thousands separator, the currency symbol and where it goes. localtime() converts a time and has nothing to do with locales in this sense.
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Determine Output:
#include <stdio.h>
#define a 10
void main()
{
#define a 50
printf("%d", a);
}
Answer: A
Correct answer: 50
The preprocessor works on the text in order and takes no notice of braces, so the second #define is in force by the time the printf line is expanded - and the program prints 50. Redefining a macro to a different value without an intervening #undef is not strictly conforming, so expect a warning.
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The header file assert.h of the C Standard Library defines ________macro.
Answer: D
Correct answer: assert
<assert.h> defines exactly one thing: the assert macro, which tests a condition and, if it is false, prints the expression, the file and the line and calls abort(). Defining NDEBUG before the include turns every assertion into nothing, which is how they are removed from a release build.
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Data written into a file using fwrite() can be read back using fscanf()
Answer: B
Correct answer: False
fwrite writes data in its binary representation, while fscanf reads formatted text. The two do not match: an int written by fwrite is four raw bytes, not the digits %d expects. Data written with fwrite must be read back with fread.
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The itoa function can convert an integer in decimal, octal or hexadecimal form to a string.
Answer: A
Correct answer: Yes
itoa(value, buffer, base) takes a base as its third argument, so it will produce the decimal, octal, hexadecimal or binary representation. It is not a standard C function - it belongs to the Turbo C and Microsoft libraries - and sprintf is the portable substitute.
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The function strlen() includes the terminating null character in the length it returns.
Answer: B
Correct answer: False
strlen() counts only the characters before the terminating null, so strlen("abc") is 3. The array holding that string nevertheless needs 4 bytes, which is why sizeof and strlen give different answers.
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What will function gcvt() do?
Answer: B
Correct answer: Convert floating-point number to a string
gcvt() converts a floating-point number to a string, in the shorter of fixed and exponential notation for the requested number of significant digits. It is a non-standard function of the old Unix and Turbo C libraries; sprintf is the portable way to do the same thing.
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