1. Variables & Data types Selection Statements Additional Operators
Outlines
Variables & Data types
Selection Statements
Additional Operators
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2. Variables and DataTypes
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3. Variables/Identifiers
Names that represent values in the program
Similar to algebraic variables
All variables have a type which must be declared
E.g. int x; float y;
Type determines :
how arithmetic is preformed,
how much memory space is required.
Variables/Identifiers
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4. Data types and sizes C has a small family of datatypes.
Numeric (int, float, double)
Character (char)
User defined (struct,union)
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5. Basic Data Types The individual sizes are machine/compiler dependent.
However, the following is guaranteed:
sizeof(char)<sizeof(short)<=sizeof(int)<=sizeof(long)
sizeof(char)<sizeof(short)<=sizeof(float)<=sizeof(double)
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6. Type Conversion Implicit Explicit
Data will get automatically converted from one type to another.
Data may also be expressly converted, using the typecast operator
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7. Implicit Type Conversion
1. When data is being stored in a variable, if the data being stored does not match the type of the variable.
The data being stored will be converted to match the type of the storage variable.
Input : 11.5
What will be printed ?
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8. Implicit Type Conversion
2. When an operation is being performed on data of two different types.
The "smaller" data type will be converted to match the "larger" type.
For example, when an int is added to a double, the computer uses a double version of the int and the result is a double.
The following example converts the value of nTotal to a double precision value before performing the division.  Note that if the 3.0 were changed to a simple 3, then integer division would be performed, losing any fractional values in the result. (try it )
int nTotal ; double average ;
average = nTotal / 3.0;
3. When data is passed to or returned from functions.
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9. Explicit Type Conversion
The following example converts the value of nTotal to a double precision value before performing the division. ( nStudents will then be implicitly promoted, following the guidelines listed above. )
average = ( double ) nTotal / nStudents;
Note that nTotal itself is unaffected by this conversion.
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10. Variables and Variable Definitions
Naming rules:
Variable names can contain letters,digits and _
Variable names should start with letters.
Keywords (e.g., for,while etc.) cannot be used as variable names
Variable names are case sensitive. int x; int X declares two different variables.
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11. Pop quiz (correct/incorrect):
int money$owed;
int total_count
int score2
int 2ndscore
int long
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12. Variable declaration The general format for a declaration is
type variable-name [=value] ;
char x; /∗ uninitialized ∗/
char x=’A’; /∗ intialized to ’A’∗/
char x=’A’,y=’B’; /∗multiple variables initialized ∗/
char x=y=’Z’; /∗multiple initializations ∗/
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13. Constants
The const qualifier is used to tell C that the variable value can not change after initialisation.
Constants are literal/fixed values assigned to variables or used directly in expressions.
Examples:
const char letter = ‘a’;
const float pi= ;
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14. Branching/ Selections
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15. Branching forms (1) If Statement (3) Nested If..else Statement
if (expression)
{Block of statements; }
if (expression)
{ Block of statements; }
else if(expression)
{ Block of statements; }
else
(2) If ..else Statement
if (expression)
{Block of statements; }
else
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16. 1. if Selection statement
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17. 2. if…else Selection statement
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18. Conditional operator ?:
The( ? : ) operator is just like an if ... else statement except that because it is an operator you can use it within expressions.
? : is a ternary operator in that it takes three values, this is the only ternary operator C has.
? : takes the following form:
if condition is true ? then X return value : otherwise Y value;
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19. Conditional operator ?:
if condition is true ? then X return value : otherwise Y value;
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20. If..else vs ?: max = x >= y ? x : y ; if ( x > = y ) max = x ;
max = y ;
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21. Nested if...else Statements
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22. Nested if...else Statements
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23. Nested if...else Statements
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24. switch statement limited by switch( expression ) { }
case constant-expression1: statements1; break;
[case constant-expression2: statements2; break;]
[case constant-expression3: statements3; ;break;]
[default : statements4;] }
limited by  
The expression can be integer or char
and cannot be float or any other data type.
No two case statement constants may be the same.
Character constants are automatically converted to integer.
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25. switch statement
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26. Operators
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27. Assignment Operators
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28. Increment and Decrement Operators
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29. Increment and Decrement Operators
For Example :-
int i, j = 2 ;
i = ++ j ; /* prefix :- i has value 3, j has value 3 */
i = j++ ; /* postfix :- i has value 3, j has value 4 */
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30. Nouf Aljaffan (C) 2018