C programming part4

C_Programming
Part 4
ENG. KEROLES SHENOUDA
1

Advanced Data Types: Arrays
 Array is a single variable that able to hold several values.
Programmer can set or get specific
value in the array.
To define an array variable containing 100 (float) values:
2

Arrays
 The position of each value is called the index. The index of the first value is 0,
which means
if the array contains 10 items the index range from 0 to 9.
 Dealing with array elements is very similar to normal variables; you can assign
a value to any item or assign any item to other program variables. Following
code illustrates this idea:
3
float degrees[100];
float x=9.9;
float y;
//assign x value to the fifth item
degrees[4] = x;
//assign fifth item to y
y = degrees[4];
//scan eighth item from user
scanf("%f", &degrees[7]);
//print eighth item from user
printf("The eighth item value is %f", degrees[7]);

Lab: Store and Print 10
Students Degrees
 shows how to scan 10
students degree from user,
stores them in a single
area, and then prints them.
4

Arrays
 Initializing the array:
When the array is defined, there is no data assigned to their elements.
Assigning initial
values for array elements is called initializing the array. Following code section
shows how
to initialize the array:
8

Lab:Calculate Polynomial
Value for a Set of Inputs
9
the program works
correctly, however it
appears that code size
contains many
repeated sections, each
section for each value. If
the number of values
increases code size
increases.
Alternative solve it
using Arrays and
Loops

Lab: Calculate the Maximum of
the Array
float degrees[] = {75.5, 88.0, 89.5, 23.5,
72.0,63.5, 57.5, 62.0, 13.5, 46.5};
11
printf ("=========>>>>>> Part2 descending order n");
printf ("=========>>>>>> Part3 ascending order n");

Following code section shows how to
use 2D arrays:
18

LAB: Calculate and Print the Transpose
of 3x3 Matrix
19

Strings
 String is a set of several consecutive characters; each character can be
represented in C language by a (char) data type.
 This means that string value can be represented by an array of (char)
21
Above code shows how to store “hello” string letters in array.
The last letter is sited with zero value (null termination), this value is
important to tell the computer that the string is
terminated before this item.

Printing String Value
 “text” variable contains 100 (char) value, only
first 5 places is used to hold the word “hello”
and
 the sixth place is used to hold the null
termination.
 In printf, “%s” is used to inform the program
that it will print a string value.
 Important: printf uses the null termination to
end the printing operation. If the null
termination is not used, the program continues
printing the following memory contents until
it reach a zero.
22

Scanning String Value 26
 scanf is used with “%s” to scan string input
from keyboard. However there is a problem?
 scanf takes only the first word in the input
text and leave the rest.

C language provides a solution for above
problem using gets function
27

Copy String to String 30
There is another
solution to above
problem using strcpy
function. strcpy takes
both the
destination and the
source strings and
performs the coping
operation internally.

Changing String Case
 strlwr function changes all string letters to the lower
case.
Ex: “AhMed” “ahmed”
 strupr function change all string letters to the upper
case.
Ex: “aHmeD” “AHMED
33

Comparing Two Strings
 strcmp function compares two strings and produces one of three results:
 if the two string are identical it gives 0
 if the first string is lower in the alphabetic order it gives -1
 if the second string is higher in the alphabetic order it gives 1
“ahmed” and “ahmed” 0
“ahmed” and “amgad” -1 because the second letter „h‟ is less than „m‟
“maged” and “aya” 1 because the first letter „m‟ is greater than „a‟
strcmp differentiate between capital and small letters which means “MAGED” is
less than “ahmed”, because the ASCII code of the capital letters is lower than the ASCII
code of the small letters. To solve this problem you can change the case of both strings
to the same case then use strcmp function. Alternatively you can use stricmp
function which performs the
comparison independent on the string case
35

Converting String to Integer Value 37
The variable text contains 4 ASCII letters „1‟, „0‟, „2‟, „5‟. The statement (x + text) is
completely wrong, because text is string and not a number, computer cannot understand
string contents directly.
atoi function helps computer to convert string to a number of type (int) if it is applicable
otherwise it gives zero, for example:
“1025”  1025
“120KG”  120
“The Cost is 30”  0

Converting String to Integer Value 38

Converting String to Real Value
 atof function helps computer to convert string to a number of type (float) if it
is applicable
otherwise it gives zero, for example:
“10.25” > 10.25
“1.2KG” > 1.2
“The Cost is 3.5” > 0
39

Follow Chapter 4/5:
Controlling Program
Flow
C PROGRAMMING FOR ENGINEERS, DR. MOHAMED SOBH
41The next Part we will talk about Variables Scope

References 42
 The Case for Learning C as Your First Programming Language
 A Tutorial on Data Representation
 std::printf, std::fprintf, std::sprintf, std::snprintf…..
 C Programming for Engineers, Dr. Mohamed Sobh
 C programming expert.
 fresh2refresh.com/c-programming

C programming part4

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