Download C Programming Fundamentals: Math, Control Structures, and Arrays and more Study notes Engineering in PDF only on Docsity!
ENGR 0012 – Dr. Lund’s 10am Section
March 13 & 15, 2007
• Section 5.3 – Basic Mathematical Operations
– Arithmetic operations
– Assignment operators
– Mathematical functions (<math.h>)
• Section 5.4 – Program Control
– Branching (IF & SWITCH-CASE)
– Looping (FOR, WHILE, & DO-WHILE)
– Using FOR loops with arrays
• Summary of String Concepts
Arithmetic Operations
• + - * / follow same rules of precedence as Matlab
• Must maintain consistency in how variables are declared
and used
• A number without a decimal point will be treated as an
integer, until multiplied or divided by a real number
• This can cause problems…
Ex: double a;
a = 1/3 +1/3 + 1/3;
#include <stdio.h> void main(void)
/* This program illustrates importance of decimal point */ { double a, b;
a=1/3+1/3+1/3; printf("a = %lf\n", a);
b=1./3+1./3+1./3; printf("b = %lf\n", b); }
Arithmetic Operations
• Bonus arithmetic operators:
– i++, ++i (increments i by one, i = i + 1)
– k = i++ is same as k = i; i = i + 1 (post-increment)
– k = ++i is same as k = i +1 (pre-increment)
– % gives remainder of one integer divided by another
• Math functions included in <math.h> library:
– pow(x,y)
– sin(x), cos(x), tan(x), sinh(x), cosh(x), tanh(x)
– log(x), log10(x)
– exp(x)
– abs(x)
Increment/Decrement
- For integer math only!
- Preincrement (++a) will
increment the variable by
1 and then print the
output
- Post increment will print
the output and then
increment by 1
decrementing by one
#include <stdio.h>
main()
int a = 10;
++a; /* same as a = a + 1; */
printf(“a = %d\n”, a);
printf(“a = %d\n”, ++a);
a++;
printf(“a = %d\n”, a);
printf(“a = %d\n”, a++);
a--;
printf(“a = %d\n”, a);
printf(“a = %d\n”, a--);
IF Control Structures in C
• Simple if structure:
if (condition)
{ statement(s)}
• Relational operators Logical Expressions
< >! NOT
<= >= && AND
= =! = || OR
• Example:
if ( x <= 10.0)
y = x*x;
printf(“Whatever…”);
If – Else and If – Else if - Else
if ( b > 1)
statements;
else
statements;
else
statements;
statements;
else if (a = = 0)
statements;
else if (b = = 0)
statements;
else
statements;
Note nesting.
Example
#include <stdio.h> void main(void) { int option;
printf("Please type 1, 2, or 3\n" "1. Breakfast\n" "2. Lunch\n" "3. Dinner\n"); scanf("%d",&option);
if(option==1) { printf("Good morning\n"); printf("Order breakfast\n"); } else if (option==2) { printf("Order lunch\n"); } else if (option==3) { printf("Order dinner\n"); } else { printf("Order nothing\n"); } }
Type in this code:
SWITCH / CASE structures
• switch ( variable )
case value1 : statement;
statement;
break;
case value2 : statement;
statement;
break;
default:
statements;
Note:
1. location of braces
2. colon after value
3. break;
4. default:
Simple for loop structure
• i = control variable
• Control variable must be declared in program
• for loop expression within parentheses contains three
components:
• i = 1; Initialization expression
(Occurs at beginning of first pass through loop)
• i <= 10; Continuation or test expression
(Loop continues if this expression is TRUE)
• i = i + 1 Increment Expression
(Occurs after statements are completed)
for (i = 1; i <= 10; i = i + 1)
statements
Some variations on loop expression…
• for (i = start; i < end; i = i + 1)
i, start, end must be declared
• for (test = 10; test >= 1; test = test –1)
loop variable can start high to low
• for (k = 2; k < 100; k = k * 2)
loop variable can be incremented in any way
• for (j = 1; j <= finish; j++)
increment expression can be written in short
form:
j++ is same as j = j + 1
j- - is same as j = j – 1
j+=2 is same as j = j + 2
j*=2 is same as j = j * 2
Assignment Operators
x += 2 is equivalent to x = x + 2
x -= 3 is equivalent to x = x – 3
x *= -5 is equivalent to x = x * -
x /= 7 is equivalent to x = x / 7
x %= 4 is equivalent to x = x % 4
- Convenient shortcuts and they execute faster as well
Simple for loop example
/* sum the first n digits (1, 2,.. ., n) */
#include <stdio.h>
main() { int count, /* the loop index / n, / the number of digits (number of passes) / sum; / the cumulative sum */
printf("Sum the first n digits\n\n"); printf("How many digits? "); scanf("%d", &n);
sum = 0; for (count = 1; count <= n; count++) { sum = sum + count; }
printf("\nThe sum is %d\n", sum); }
One last loop… the do / while loop
General format:
do
statements;
} while (test expression);
#inlcude <stdio.h>
main ()
int j = 4;
do
printf(“Old j = %d, “, j);
j = j - 1;
printf(“new j = %d\n”, j);
} while (j >= 1);
while loop vs. do / while loop
#inlcude <stdio.h>
main ()
int j = 4;
do
printf(“Old j = %d, “, j);
j = j - 1;
printf(“new j = %d\n”, j);
} while (j >= 1);
#inlcude <stdio.h>
main ()
int j = 4;
while (j >= 1)
printf(“Old j = %d, “, j);
j = j - 1;
printf(“new j = %d\n”, j);
The only difference between a while loop and a do/while loop is that if the
test expression is FALSE at the beginning of a while loop, the loop will not
execute; whereas with the do/while loop, if the expression is FALSE to begin
with, the loop would be executed once before exiting.
An array is a collection^ of elements that have the same name.
All elements must be of the same data type.
An integer-valued subscript is used to access an individual array element.
Subscripts range in value from 0 to n - 1 , where n is the size of the array.
x[0] x[1] x[2] x[n−2] x[n−1]
“1-d Arrays” (vectors)
Contiguous Physical Memory Locations…
Declaring 1-D Arrays
#include <stdio.h>
void main(void) {
float x[100], y;
int values[50], m, n;
- Defines a 100-element array called x.
- All 100 elements are floating point.
- Individual array elements are x[3], x[i], x[j + 2], etc. (where i and j are integer variables). Note: 3, i and j + 2 are subscripts.
- Subscript values range from 0 to 99. First element is x[0]
- Defines a 50-element array called values.
- All elements are integers.
- Subscript values range from 0 to 49.
Type Name Length temp[0] temp[1] temp[2] temp[3] temp[4]
int temp [100];
Memory Addresses: 1000 1004 1008 1012 1016
?????
2-Dimension Arrays
• Syntax for a 2-D array
matrix_a[rows][cols]
• Example
• matrix_a[2][3] = -
matrix_a
- Note separate brackets for each dimension
- Rows are specified in first set of brackets
Storage of 2-D Arrays
• Data is stored in memory by rows, i.e.
right most variable varies first
• For x [3][4] which has 3 rows, 4
columns…
x[0][0] x[0][1] x[0][2] x[0][3] x[1][0] x[1][1]
Memory Address (4 bytes per number)
x[1][2] x[1][3] x[2][0] …
FF74 FF78 FF7C FF80 … (hexadecimal address system)
Remember! In C, the first element of an array dimension is a zero
Declaring 2-D Arrays
There are several ways 2-D arrays can be
declared…
- double a[2][3]; //Not initialized; max of 2 rows, 3 columns
- double a[2][3]={1,2,3,4,5,6}; //Initialize on one line
- double a[2][3]={{1,2,3}, {4,5,6}}; //Initialize by rows in { }
- double a[ ][3]={1,2,3,4,5,6}; //Let C determine number of rows
- double a[2][3]={ }; //Initialize with all zeroes
Input / Output with 2-D Arrays
#include <stdio.h> #define N 3
main() { double a[N][N]; int i, j;
printf("\n\nPlease enter the elements of MATRIX A:\n"); for (i=0; i<N; i++) { for (j=0; j<N; j++) { printf("Enter element in ROW=%d, COL=%d: ", i+1, j+1); scanf("%lf", &a[i][j]); } }
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