2.1.2-Designing, Creating and Refining Algorithms

Input

The data entered by a program, either by a user or the processor itself.

process

The steps that a program uses to carry out a specific task.

output

The data that is displayed to the user after certain steps of a program have been completed.

structure diagram

A diagram that shows tasks that have been broken down into subtasks in order to make it easier to solve

Algorithm

A specific set of instructions a computer can follow in order to make a problem easier to solve

Flowchart

a visual representation of an algorithm that clearly shows input, processes and outputs

Sub-problem

a smaller problem that is part of a larger problem

Pseudocode

A universal programming language that is a mix of English and programming languages.

Variable

A container in an algorithm that can change without the actual code being changed

Constant

A container in an algorithm that doesn't change unless the code is altered.

sequence

the order in which the tasks are followed in an algortihm

Selection

A decision in the program, where different conditions result in different tasks being carried out.

Iteration

When tasks in a program are repeated

Syntax Error

An error in the language of the program. The computer cannot perform the program if there are syntax errors.

Logic error

An error in the logic of the program. The computer will still carry out the tasks, but they will not be the intended tasks.

Trace Table

A table that allows you to go through each step of an algorithm to ensure there are no logic errors and the program is running as desired.

start (flowchart)

rectangle with curved edges

input/output (flowchart)

parallelogram

process (flowchart)

rectangle

decision (flowchart)

diamond

subprocess (flowchart)

rectangle with lines along two edges

and/or/not

capitalised

all text should be...

lowercase

how many statements per line?

1

what should the variable names be?

meaningful

example of logic error

-incorrect comparison operator
-incorrect arithmetic operator

example of syntax error

-missing parenthesis
-misspelled words

pseudocode FOR loop

for x\= 1 to 10
print (x)
next x

pseudocode WHILE loop (definite)

x\=0
while x

pseudocode WHILE loop (indefinite)

num1\=10
num2\=input("enter your guess: ")
while num2 !\= num1 then
print ("incorrect")
num2\=input("enter your guess: ")
endwhile
else
print ("correct")

pseudocode DO UNTIL loop

num1\=10
num2\=input("enter your guess: ")
do:
print ("incorrect")
num2\=input("enter your guess: ")
until
num1\=num2