Printf sum of all elements in a is dn 13 sumelements

11
}
12
printf( "sum of all elements in a is %d\n",
13
sumElements ( a, size ) );
14
printf( "sum of first 5 elements in a is %d\n",
15
sumElements ( a, 5 ) );
16
printf( "sum of last 5 elements in a is %d\n",
17
sumElements ( a+5, 5 ) );
18
return 0;
19
}
20
21 // adds size many elements of array a
22 // assumption : the size of the array is at least equal to size
23
int sumElements ( int
*
a, int size ){
24
int sum = 0;
25
int i;
26
for (i = 0; i < size; i++ ) {
27
sum = sum + a[i];
28
}
29
return sum;
30
}
See sum.c and sum 2.c for this code and its version that passes int a[] as a parameter to the function.
Something to Think About:
DNHI : Modify the code above to check your answers to the following questions:
1) What happens if sumElements() function modifies the content of array a ? Do changes affect the array declared in
2) What happens if the size paramter passed to the sumElements() function exceeds the size of the declared array a ? Try it by

CSCI-UA 201
Lecture 2: Introduction to C Programming Language
Joanna Klukowska
[email protected]
char tmp;
// 1 byte of storage
int i;
for (i = 0; i < size; i++) {
// for every byte : swap the byte
tmp = x[i];
x[i] = y[i];
y[i] = tmp;
}
}
See swap generic.c for an example of use of this function.
5 Strings in C
Two strings walk into a bar and sit down. The bartender says, ”So what’ll it be?”
The first string says, ”I think I’ll have a beer quag fulk boorg jdkˆCjfdLk jk3s d#f67howe˜owmc63ˆDz x.xvcu”
”Please excuse my friend,” the second string says, ”He isn’t null-terminated.”
A string in C is an array of characters terminated by a null character ( \ 0 ) . Every function that performs operations on strings uses
that null character. A missing null character in a string is also the source of most errors (and jokes) related to strings in C.
Whenever we have a double quoted string in a program it is stored as a string constant terminated by a null character. For example:
printf("Hello World!\n");
Writing
char h[] = "hello";
creates and array of 6 characters (yes, 5 letters + a null character). It is equivalent to writing
char h[6]= "hello";
Note that the following lines will compile as well and sometimes even run without obvious problems (at first)
char