Dec 1998 CA208: 'C' Programming (Question 1)

(a)	Name two type modifiers other than unsigned.	[2]
	Any two of the following: signed, long or short.
(b)	Name two storage class modifiers other than static.	[2]
	Any two of the following: extern, auto, register, const, or volatile.
(c)	Describe what a structure and a union are, and identify the difference between the two.	[3]
	A structure is an ordered fixed size sequence of named objects (1 mark). A union is an overlapping sequence of named objects (1 mark). The difference between the two is the size of a structure is the sum of the sizes of its constituent parts, and the size of a union is the size of the largest part (1 mark).
(d)	Create appropriate declarations for each of the following variables:
	(i) digits, an array of 10 unsigned integers.	[1]
	unsigned int digits[10];
	(ii) apc, an array of 20 pointers to characters.	[1]
	*char apc[20]; or char (apc[20]); Note: the [] have higher precedence that , so in the absence of parentheses, the array descriptor is applied first, then the pointer descriptor.**
	(iii) pacc, a pointer to an array of 20 characters.	[2]
	*char (pacc)[20]; or char pacc[][20];**
(e)	Write a procedure maxpair that takes two integer valued parameters x and y as its arguments. The effect of the procedure should be to change the values of x and y so that x holds the larger of the two values, and y the smaller.	[4]
	Two definitions of the maxpair procedure are shown below: void maxpair(int x, int y) { int temp; if (x < y) { temp = x; x = y; y = temp; } } void maxpair(int x, int y) { int temp; if (y > x) { temp = y; y = x; x = temp; } } and the following marking scheme should be used: one mark for the procedure declaration. If the declaration just contains int x, int y, then award no marks, but mark the points below as though any references to x where actually x. one mark for initiating a swap if the first argument is smaller than the second.* one mark for assigning one of the arguments to the temporary variable. *one mark for the correct assignments to x and y.* no marks should be deducted for trivial syntactic errors.
(f)	Trace the following code segment and produce the output: void main(void) { int num_list[5] = (1,2,3,4,5); int i, one, two; one = &num_list[1]; two = num_list; (one-1) = 42; two = 66; printf("First = %d\n", one); printf("Second = %d\n", num_list[0]); one = one + 3; two = (++two) + 1; printf(""Third = %d\n", one); printf("Fourth = %d\n", *two); for(i=0; i<5; i++) printf("%d ", num_list[i]); }	[5]
	One mark for the correct numbers appearing on each line below: First = 2 Second = 66 Third = 5 Fourth = 3 66 2 3 4 5 Do not deduct marks for incorrect typesetting of the answer. i.e., if the second answer is written as Second = 66 instead of Second = 66, then marks should still be awarded.