1. Data Types, Identifiers, and Expressions
Topics to cover here:
Data types
Variables and Identifiers
Arithmetic and Logical Expressions
Programming Fundamental Slides

2. Programming Fundamental Slides
Data Types
A data type provides a method of modeling or representing a particular set of values and determines what operations can be performed on those values.
Programming Fundamental Slides

3. Programming Fundamental Slides

4. Data Types in The Algorithmic Language
String values (e.g. “ABC” , “computer”, “960”)
NOTE: In C++ language, some of the operations have different symbols.
Programming Fundamental Slides

5. Identifiers, Locations, and Variables
Memory: It is a part of the computer that has many locations (of fixed size) used to store values (data) and instructions.
Programming Fundamental Slides

6. Identifiers, Locations, and Variables.. cont.
Identifiers (Names):
- Use meaningful identifiers (names) to represent
data in your program.
- Identifiers are used to refer to memory
locations: to store data in them or retrieve data
from them.
The rule of defining an identifier:
(1) It may contain
letters (A .. Z , a .. z ) ,
digits (0, 1, 2, …, 9), and
underscore ( _ ).
(2) It should begin with a letter.
Programming Fundamental Slides

7. Identifiers, Locations, and Variables.. cont.
NOTES:
Some programming languages are case sensitive. That is the uppercase identifiers are different than lowercase identifiers (as in C++).
In programming languages, some words cannot be used as identifiers in your program. Such words are called reserved words (or keywords) that have special use.
Programming Fundamental Slides

8. Reserved words (or keywords) in c++
main if
else
while do
for

9. Identifiers, Locations, and Variables.. cont.
Examples of valid identifiers:
area , length, X , Y1, abc, d3, st_number
{ these all begin with a letter }
Examples of invalid identifiers:
2Y { begins with a digit }
Ali’s { contains the symbol ‘ }
st-age { the symbol - is not underscore }
while { it is a keyword }
ab cd { it has a space }
Programming Fundamental Slides

10. Identifiers, Location, and Variables.. cont.
-The name of the location is the variable name.
-The location content is the value of the variable
- You can change the content of the variable at any
time in the statements of the algorithm.
e.g.
Name of the location Inside Memory location
employee_name “Ali Ahmed”
age
hourly_rate
Programming Fundamental Slides

11. Identifiers, Location, and Variables.. cont.
Constants:
- You can use a constant identifier in your algorithm to indicate a constant data.
You CANNOT change the content of the constant identifier.
Use the keyword CONST to indicate a constant identifier.
e.g.
CONST pi = 3.14
Here, pi is a constant identifier that cannot be changed
Programming Fundamental Slides

12. Expressions EX: T MOD 2 gives 0 if T is any even number, and
Arithmetic Expression:
- It is composed of operands and arithmetic operations
- Arithmetic operations:
- Operands may be numbers and/or identifiers that have numeric values
Its result is a numeric value
EX : gives 7
EX: T MOD 2 gives 0 if T is any even number, and
1 if T is any odd number

13. Expressions .. cont. Logical Expression:
- It is called also Boolean expression.
- It is composed from operands and operators.
- Operands are identifiers that have logical values
- Its result is a logical value (true or false) (see later).
- Operators are logical:
EX:
where A, B are defined logical
Note: In C++, there is no specific data type to represent “true” and “false”. C uses value “0” to represent “false”, and uses non-zero value to stand for “true”.

14. Expressions .. cont. - It is composed from operands and operators.
Relational Expression:
- It is composed from operands and operators.
- Operands may be numbers and/or identifiers
that have numeric values
- Its result is a logical value (true or false).
- Operators are relational operators:
EX:

15. Programming Fundamental Slides
Expressions .. cont.
NOTES
A relational expression may contain arithmetic sub-expressions,
e.g. ( ) < (12 * 4 )
2) A logical expression may contain relational and arithmetic sub-expressions,
e.g.
x AND y AND ( a > b )
(2 + t ) < (6 * w ) AND ( p = q )
Programming Fundamental Slides

16. Programming Fundamental Slides
Operator Precedence
Expressions are evaluated according to the precedence rule.
Precedence Rule:
- Each operator has its own precedence that indicates the order of evaluation.
- If the expression has operators of the same precedence, then the evaluation starts from left of expression to the right.
Programming Fundamental Slides

17. Operator Precedence .. cont.
Description
Operator In
C++
Operator In pseudo code
Higher
parentheses (
*, /, %
*, /, MOD
Binary plus, binary minus
+ , -
<, <=, >, >=
<, , ≤, >, ≥
Equal, not equal
== , !=
= , ≠
&&
AND || OR
Lower
Assignment = 
Programming Fundamental Slides

18. Programming Fundamental Slides
Examples
Find the value of the following expression:
(1) * / 4 16 4
(This is the final result)
Programming Fundamental Slides

19. Programming Fundamental Slides
Examples .. cont.
( ) / 12 3 9
(this is the final result)
Programming Fundamental Slides

20. Evaluating Logical Expressions
The truth table
AND table
AND True False
True True False
False False False
Programming Fundamental Slides

21. Evaluating Logical Expressions.. cont.
(2) OR table
OR True False
True True True
False True False
(3) NOT table
NOT True False
False True
Programming Fundamental Slides

22. Examples on Logical Expressions
If x = True, y = False, z = False, find the value of the expression x AND y OR z
x AND y OR z
False
False (the final result)
Programming Fundamental Slides

23. Examples on Logical Expressions .. cont.
(2) If a = 3, b = 5, x = true, y = false, find the value of the expression: ( a < b ) AND y OR x
( a < b ) AND y OR x
True
False
True (the final result)
Programming Fundamental Slides

24. Programming Fundamental Slides
Short circuiting:
Short circuiting means that we don't evaluate the second part of an AND or OR unless we really need to.
Programming Fundamental Slides