1. Further C Programming Variable types Loops Conditional statements
Local and Global variables
Arrays
Pointers

2. Variable Types Types char character
short short integer to 32767
int integer -/+2,147,483,647
long int long integer ~ -/+ 9E18
float floating point 1.2E-38 to 3.4E38
double double precision 2.2E-308 to 1.8E308

3. for loop Can set up loops to repeat sections of code
for (count = 1 ; count <=3 ; count++) {
printf("%d \n", count); }
count++ is short hand for count=count+1

4. While Loop
Useful when we don’t know how many times the loop will repeat. Eg
while (a>0) {
fscanf(fin,"%d %d",&a,&b) ;
c = a*b;
printf("%d * %d = %d \n", a,b,c); }
Use to read a file to the end.
while(!feof(fin)){fscanf(fin,”%d %d”,&a,&b);}

5. Conditional Statements
Most common example is the if…else construction Eg
if(mark >= 40)
printf(“pass\n”);
else
printf(“fail\n”);
Boolian operators:
= = && || !
Equals And Or Not

6. Functions and Variables
Common mathematical functions are defined in the header file math.h
# include <math.h>
Often useful to define your own functions.
Functions must be prototyped before the main() loop is reached.

7. /* and the sine of the product*/ # include <stdio.h>
/* Program to calculate the product of two numbers */
/* and the sine of the product*/
# include <stdio.h>
# include <math.h>
int product(int, int);
int main(void) {
int a,b,c;
printf ("Enter a number between 1 and 100: ");
scanf ("%d", &a);
scanf ("%d", &b);
c = product(a,b);
printf("%d times %d = %d \n", a, b, c);
printf("sin(%d times %d)= %f\n",a,b,sin(c));
return(0); }
int product(int x, int y)
int z;
z=x*y;
return(z);

8. Variables declared within a function are local to that function.
i.e. their values are only know within the function.
Changes made to the variables are not known outside the function.
Variables declared above the main() loop are global variables.
i.e. their values are known anywhere in the program.
Changes can be made anywhere in the program.

9. /* and the sine of the product*/ # include <stdio.h>
/* Program to calculate the product of two numbers */
/* and the sine of the product*/
# include <stdio.h>
# include <math.h>
int product(void);
int a,b;
int main(void) {
int c;
printf ("Enter a number between 1 and 100: ");
scanf ("%d", &a);
scanf ("%d", &b);
c = product();
printf("%d times %d = %d \n", a, b, c);
printf("sin(%d times %d)= %f\n",a,b,sin(c));
return(0); }
int product(void)
int z;
z=a*b;
return(z);

10. Arrays
If you have lots of variables of the same type it is inconvenient to have to define each separately
Eg. data1, data2, data3,………
Arrays are a way of storing a set of like variables
Eg double data[100];
Values can be assigned directly
Eg. double x[4]={23.4, 54.6, 66.1, 76.2}
or using loops
Eg for(i=0; i<4;i++)
x[i]=sin(i*M_PI/4);

11. For an array x[N] of size N, the elements are labelled
x[0], x[1], x[2], …… x[N-2], x[N-1]
Can be used just as other variables
Eg.
Sum2=0;
for(i=0;i<N;i++)
sum2=sum2+x[i]*x[i];
A common mistake is to access array elements that don’t exist.
Eg. x[N]

12. Multidimensional Arrays
int random_array[10][10][10];
for(a=0;a<10;a++) {
for(b=0;b<10;b++)
for(c=0;c<=10;c++)
random_array[a][b][c]=rand(); }

13. Pointers
When we define a variable x, the computer labels a part of the memory x and stores the value of x in that part of memory.
We can then use x as a variable in our calculations.
Another way of accessing the variable x would be to know where it is stored, i.e. its address.
We can define a “pointer” to x as a new type of variable that stores the address of the variable x.

14. #include <stdio.h>
int main(void) {
double x;
double *p;
p=&x;
x=2.0;
printf(“x=%f\n”, x);
*p=3.0;
return(0); }

15. Pointers can be passed to functions to allow them to change more than one variable.
Eg.
# include <stdio.h>
void increase(int *, int *, int *);
int main(void) {
int x,y,z;
increase(&x, &y, &z);. }
void increase(int *px, int *py, int *pz)
*px=*px+1;
*py=*py+1;
*pz=*pz+1;

16. Pointers and arrays are closely related.
x[0], x[1], x[2]……. are variables (eg. doubles).
&x[0], &x[1], &x[2]……are their addresses.
BUT
x is a pointer to x[0].
Arrays elements can be accessed in two ways
x[i] is the same as *(x+i)

17. Arrays can be passed between functions simply by passing a pointer to the first array element.
Much quicker than copying one array to another.
If you change elements of the array within the function, these changes will be known everywhere in the code.

18. #include <stdio.h>
#define N 5
void mean(double *);
int main(void) {
int i;
double x[N];
for(i=0;i<N;i++)
printf(“input value %d: ”,i);
scanf(“%f”,&x[i]); }
mean(x);
return(0);
void mean(double *x) {
int i;
double sum;
sum=0.0;
for(i=0;i<N;i++)
sum=sum+x[i];
printf(“Mean = %f\n”,sum/(N)); }