Strings String Basics MCQ

The compiler sizes the array from the literal, including the terminating '\0': 5 letters + 1 = 6 bytes. strlen(s) would be 5.

C (unlike C++) allows the literal to fill the array exactly, dropping the terminator. s is then just 5 chars, and passing it to strlen() or printf("%s") reads past the end.

gets(buf) is never told how big buf is, so a long line overflows it – a classic security hole. Use fgets(buf, sizeof buf, stdin).

a is a new 3-byte array initialised from the literal. p points at the literal itself, which compilers usually place in read-only memory. Declare it const char *p. Also sizeof p is 8, sizeof a is 3.

The standard only promises the sign: negative, zero or positive. Many libraries return the difference of the first differing bytes, so test < 0, never == -1.

strncpy() copies at most n characters and adds a terminator only if the source is shorter than n. Here it copies "Lear" and stops, so d is not a string until you set d[3] = '\0'.

snprintf(buf, size, fmt, …) writes at most size bytes including the terminator, and returns the length it needed so truncation can be detected. sprintf() has no size limit.

strtok() replaces each delimiter it stops at with '\0' and remembers where it stopped. So the input must be writable, empty fields are skipped, and it is not safe to use for two strings at once.

The ctype functions take an int that must be EOF or a value of unsigned char. Where char is signed, a byte such as 0xE9 (é in Latin-1) becomes −23 – undefined behaviour, and a real crash on some libraries.

strlen() counts bytes up to '\0'. In UTF-8, é is two bytes (0xC3 0xA9), so the 5 visible characters take 6 bytes. Counting characters needs UTF-8 decoding.