cs chapter 5

What are the requirements of a well written algorithm

• it should be free of logic errors

• It should be easy to code in any high-level language

define execution

the process by which a computer carries out the instructions of a computer program

What are some uses of variables

• controlling the number of times a loop is executed

• determining which branch of an IF statement is taken

• keeping running totals

• holding user input

Do you need to specify data types of variables?

It is not necessary in pseudocode, however data types become much more important in high level language programming as the data type of a variable determines the operations that can be performed on it.

what is type coercion

the process of converting the value stored in a variable from one data type to another (implicitly)

Type coercion is when the data type of a variable changes during program execution (implicit so it happens automatically e.g if an integer and real value are used in a calculation the resulting value will be a real value)

what is type casting

the process of converting the value stored in a variable from one data type to another (explicitly)

Type casting is when the data type of a variable is converted during program execution (explicit so the user needs to state e.g may = int(x))

define initialize

to set variables to their starting values at the beginning of a program or subprogram

assignment statement

the command/ statement used to change the value of a variable that has been initialized

it is also the SET … TO command used to initialize variables in pseudocode

assignment statement

the command/ statement used to change the value of a variable that has been initialized

it is also the SET … TO command used to initialize variables in pseudocode

What does a variable (such as a loop counter) that is intended to hold a running total need to be in order to use it?

the variable should always be initialized to a starting values (e.g 0)

some programming languages won’t execute if the programmer fails to do this

others may execute but may well produce some unexpected results (logic error)

selection

a construct that allows a choice to be made between different alternatives

used to create a branch in a program

the computer selects which branch to follow based on the outcome of a condition

define nested IF statement

a nested IF statement consists of one or more IF statements placed inside each other. A nested IF statement is used when there are more than two possible courses of action

for Pearson edexcel pseudocode, when creating nested IF statements, you have to ensure that each one is completed with an END IF at the correct indentation level

what is order of precedence for logical operators ?

AND

NOT

OR

define relational operator

an operator that tests the relationship between two entities

define logical operator

a Boolean operator using AND, OR and NOT

definite iteration

when the number of iterations is known in advance

using a for loop (python + pseudocode) and repeat loop

nested loop

a loop within a loop

each iteration of the outer loop causes the inner loop to be executed until completion

indefinite iteration

when the number of iterations is not known in advance

repeated until specific condition is met

while loop (python) repeat until (pseudocode)

Random numbers

used to make an event random

python has a random module

(Import random

random has 3 different forms:

what happens when a variable is initialized

When a variable is declared, the computer gives it a location in its memory. Initially this location is empty so before a variable can be used, it has to be given a value