Chapter 3 cards Flashcards
What is an algorithm?
A procedure for solving a problem in terms of:
- the actions to execute
- the order in which these actions execute
What is program control?
It specifies the order in which statements (actions) execute in a program.
Python does this with Python’s control statements
A(n) ______________ is a procedure for solving a problem. It specifies the ________ to execute and the _______ in which they execute
Algorithm, actions, order
What is Pseudocode?
An informal language that helps develop algorithms without having to worry about the strict details of Python synthax. Similar to everyday English. Helps you ‘think out’ a program before attempting to write it in a programming language
- Text describes what the program should do
- Convert text to Python with Python equivalent
T/F
Pseudocode is a simple programming language
False
Pseudocode is not a programming language. It’s an artificial and informal language that helps you develop algorithms
Define
Sequential execution
Where statements in a program execute in the order in which they’re written
Define
Transfer of control
A Python statement that enables you to specify that the next statement to execute may be other than the next one in sequence
Explain
How is transfer of control achieved?
With Python control statements
What are the 3 forms of control that all programs be written with?
- Sequential execution
- Selection statement
- Iteration statement (repetition)
Python statements execute ‘in sequence’ unless directed otherwise
Define
Flowchart
A ‘graphical’ representation of an algorithm or a part of one
Explain
How to draw a flowchart
Draw flowchart using rectangles, diamonds, rounded rectangles and small circles that you connect by arrows called flowlines
Why is a flowchart useful?
Helps develop and represent algorithms. They show how forms of control operate.
What do we use to indicate an action in a flowchart?
We use rectangle (or action) symbol
What shows the order in which actions are executed in a flowchart?
Flowlines
What is seen at the beginning of a complete algorithm?
A rounded rectangle containing the word Begin
What is the last symbol you see in a completed algorithm?
A rounded rectangle containing the word End
When are rounded rectangles omited in an algorithm?
For a part of the algorithm, instead using small circles called connector symbols
What is the most important symbol in an algorithm?
Decision or diamond symbol which indicates that a decision is to be made, such as in an if statement
What are the 3 selection statements that execute code based on a condition (an expression that evaluates to either True or False:
- If performs an action in a condition is True or skips the action if the condition is False
- If ….. else statement performs an action if a condition is True or performs a different action if the condition is False
- If … elif….. else statements perform one of many different actions, depending on the truth or falsity of several conditions
Why is the If statement called a single-selection statement?
It selects or ignores a single action (or group of actions).
Why is the If… else statement called double-selection statement?
It selects between two different actions (or groups of actions).
Why is the If… elif… else statement called multiple-selection statement?
It selects one of many different actions (or groups of actions)
What are the 2 keywords Python uses for repetition statements (iteration)?
while and for
Define the 2 repetition statement types
- while statement repeats an action (or group of actions) as long as a condition remains true
- for statement repeats an action (or a group of actions) for every item in a sequence of items
What are the keywords discussed on this chapter that Python reserbes to implement its features, such as control statements?
if
elif
while
for
True
False
None
Note the bold words start with an uppercase letter
What is a quick summary of control statements in this chapter?
- You form each Python program by combining as many control statements of each type as you need for the algorithm the program implements
- With single-entry/single-exit (one way in/one way out) control statements, the exit point of one connects to the entry point of the next (similar to the way a child stacks building blocks – hence, the term control-statement stacking
- Control-statement nexting also connexts control statements – next chapter
You can write all programs usiing three forms of control –_____, _______ and _________
Sequential execution
Selection statements
Repetition statements
A(n) ________ is a graphical representation of an algorithm
Flowchart
