C Programming 04/5

Question 1

What is a pointer?

Answer 1

If an int variable stores an integer value, an int* variable stores the memory location of an int

Question 2

What is sizeof?

Answer 2

Gives the size of a C object
e.g
sizeof(char) == 1 (always)
sizeof(int) == 4 (usually)

Question 3

What is pointer arithmetic?

Answer 3

Another way of array indexing
e.g
a[i] == *(a+i)
&a[i] == a+i

Question 4

What are the 4 main functions to work with strings?

Answer 4

int strlen( const char *s );
• The length of s (without \0)
int strcmp( const char *s1, const char *s2 );
• Compare s1 and s2, 0 if same, -1 if s1 < s2, 1 is s1 > s2
char *strcpy( char *s1, const char *s2 );
• Copy string s2 to s1
char *strcat( char *s1, const char *s2 );
• Append s2 to s1

Question 5

What are the 2 stdio functions?

Answer 5

char *gets( char *s );
• Read input into s until \n or EOF read. Returns s.
int puts( const char *s );
• Print s followed by a newline.

Question 6

What is a struct?

Answer 6

Logical choice for storing a collection of related data items, superficially similar to a Java class

Question 7

What is a union?

Answer 7

• A union, like a structure, consists of one or more
members, possibly of different types.
• The compiler allocates only enough space for the largest of the members, which overlay each other within this space.

Question 8

Past Paper Question: Give an example of defining and using a union. Why does C provide unions?

Answer 8

union u {
int i;
double d;
};

These are a way of conserving memory, as the compiler only allocates enough space for the largest member.