FBLA COMP CPU SCI: Algorithms & ProgrammingConcepts:2:@1
What is an identifier
An identifier refers to a location in memory where the data item will be stored.
Each variable has a data type that defines
1) They type of data that will be stored at the memory location (therefore the operations that can be performed on this data item).
2) How much space will be needed for that data item.
What is the typical amount of memory of a Integer?
2 or 4 bytes.
What is the typical amount of memory of a Real / Float?
4 or 8 bytes.
What is the typical amount of memory of a Char / Character?
1 byte.
What is the typical amount of memory of a String?
1 bytes per character in string.
What is the typical amount of memory of a Boolean?
1 byte.
Declare a variable in pseudocode
Num1 <- 5
Declare a constant in pseudocode
CONST Num1 <- 5
What is initialisation
To set starting values for variables at the beginning of a program.
Where do you declare constants?
At the start of the program.
What are the two main benefits or declaring a constant?
1) When its value changes, you only have to edit it in one place rather than looking for every place in the program where you uses that number.
2) The code will be easier to read and understand because the constant's identifier will be used instead of a number.
Definition of an array
An array is a group of data items of the same data type which is stored under one identifier (name) in contiguous (one after another) memory locations.
What are the benefits of using arrays?
1) Code is easier to follow and therefore easier to debug and maintain.
2) A group of data can be easily processed using a loop.
You can "Do what" to indexes of an array?
1) Assign values to them.
2) Read values into them from the keyboard or a file.
3) Write the values stored in a box to the screen of a file.
Program a "repeat" loop in pseudocode
REPEAT
.
.
.
UNTIL (continue = "N") or (continue = "n")
What is a sequence (construct)?
Sequence is writing the steps down in the order they need to happen.
What is a selection (construct)?
IF...THEN...ELSE allows you to choose between two options. By nesting these or having several in a row you can choose between several options but this is more efficiently achieved by the CASE statement.
What is the first method of a selection (construct)?
Using multiple IF statements.
What is the second method of a selection (construct)?
Using multiple nested IF statements. Only executes the IF statement until it finds one that is true.
What is the third method of a selection (construct)?
Using a CASE statement. Much clearer than the first or second method of a selection (construct).
What is an iteration (construct)?
There are three basic iteration (loop) constructs that you will learn when you program, including FOR, REPEAT and WHILE.
Define a FOR loop
The FOR loop allows you to execute a group of steps 1 or more time, for a specific amount of times.
Define a REPEAT loop
A REPEAT loop is controlled by a condition at the end of the loop. Therefore it will always execute the following steps at least once.
Define a WHILE loop
A WHILE loop is controlled by a condition at the start of the loop. Therefore it will execute the following steps zero or more times.
What will a working algorithm always do?
It will always finish and return an answer or perform the task it was supposed to.
Why is it important to structure a system into manageable modules?
1) Different people can work on different sections at the same time.
2) Some parts may be used several times in a system.
3) Modules can be tested on their own before being put together in the whole system. Makes it easier to debug.
4) A modular system is much easier to understand and maintain later on.
Describe the structure of a structured diagram?
1) The diagram should start with a box at the top that represents the whole program.
2) The whole program can then be broken down into smaller components eg. Getting players name, playing the game in turns etc..
3) Keep on breaking the boxes down into the smallest chunk you can make.
Define a WHILE loop
A WHILE loop is controlled by a condition at the start of the loop. Therefore it will execute the following steps zero or more times.