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The Program development life cycle
Analysis The analysis stage uses abstraction and decomposition tools to identify exactly what is required from the program Design This stage uses the structure charts, flowcharts and pseudocode to develop the design of the program. Coding The program or set of program is developed using a suitable programming language and then tested to see if it works Testing The completed program or set of programs is run many times with different test data to ensure that all tasks completed work together as specified in the program Program development Life cycle is divided into five stages : Analysis, Design, Coding, Testing and maintenance
is made up of software, data, hardware, communications and people. each computer system can be divided up into a set of sub-systems. Each subsystem can be further divided into sub- systems and so on until each sub-system just performs a single action.
What is Computer System
User Input Devices Data Process Program/software Result Output Device Computer System Sub-system Sub-system Sub-system Sub-system
Breaking a problem down into smaller parts/tasks makes it far easier to understand,
solve and manage
Top down design allows several programmers or teams to work on the same
project/task, without getting in each other’s way
Each sub-system of code to be tested separately
Advantages of Top-DownDesign/decompositon
Abstraction
Abstraction keeps the key elements required for the solution to the problem and discard any unnecessary details and information that is not required.
An algorithm is a procedure used for solving a problem or performing a computation. There are two ways to represent algorithm Flow Chart Pseudocode
Algorithm
is a method of expressing an algorithm design.
It describes what the algorithm does by using English key words that are very similar to
those used in a high-level programming language
are no definitive rules for writing pseudocode but it should make sense and logically solve
the problem/task.
Once a problem has been solved logically using pseudocode, it can then be coded into an
actual programming language of choice.
Pseudocode
The program needs to remember/store a value to read and use later on
In order to store a value, the program needs to establish a memorable (named)
place.
These locations/named are called variables and constants.
Variable The identifier (name) given to a memory location used to store data. The value can be changed during program execution. Values are assigned variable using the <– operator.
Variable and Constant
Constant
- A named memory location that contains data that can be read but not changed by the program
- Values are assigned variable using the <– operator.
Variable and Constant
How to declare variable
Declare variables that are used in pseudocode.
DECLARE variable name : Data Type
- INPUT/ READ is used for the entry of data from user.
- OUTPUT/ Print display of information/result to user.
Input and output statement
Sequence is indicated by the order in which the code is written, usually top to bottom. Sequential execution is when statements are executed one after another in order. Statements are followed in sequence so the order of the statements in a program is important.
Sequence
Selection used to determine a different set of steps to execute based on a decision (condition). Code branches and follows a different sequence based on decision made by program
Selection /Conditional statements
A condition can be set up in different ways:
Using a Boolean variable that can have the value TRUE or FALSE
Using comparison operators
Boolean/Comparison/Relational Operator
**Operator Comparison
** Greater than < Less than = Equal >= Greater than or equal <= Less than or equal <> Not equal
Tests the value of a variable and compares it with multiple value (case). Once the case match is found, a block of statement associated with this case is executed. If a case match is not found, the otherwise statement is executed.
CASE … OF … OTHERWISE …ENDCASE
