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2.2 Programming V1
- Variables: Inputs, Outputs and Assignments
- Variable - Changes
throughout the program
- Constant - Fixed for the
duration of the program
- Normally in
CAPITAL letters
- In capitals to simplify debugging and
are less likely to generate mistakes as
they don'tchange during runtime
- In capitals to simplify debugging and
are less likely to generate mistakes as
they don'tchange during runtime
- Normally in
CAPITAL letters
- RAM is divided in memory locations with long
hexadecimal (but really binary) addresses
- A grid of memory locations (or cells) can hold values
- Inputs
- Programs would be useless without inputs
as they can't interact with the outside world
and always produce the same results
- Programs would be useless without inputs
as they can't interact with the outside world
and always produce the same results
- Variable - Changes
throughout the program
- Selection
- Allows a computer to "think" - make decisions
- Changes the flow of a program, depending on a set of conditions, it is
used for validation, calculation and making sense of a user's choices
- Nested Selection
- Sometimes, we can only evaluate a condition if some pre-condition is
met. We would need two selection statements, one inside the other
- The "outside" selection is the pre-condition,
while the "inside" selection is the conditon
- There is no limit on how many
selection statements we can nest
- Sometimes, we can only evaluate a condition if some pre-condition is
met. We would need two selection statements, one inside the other
- Allows a computer to "think" - make decisions
- Iteration
- For Counter (Counter-controlled)
- The loop for when we know in advance how many times we want to loop back to the start, so we keep
count against the number of repetitions that are required using a counter
- The loop for when we know in advance how many times we want to loop back to the start, so we keep
count against the number of repetitions that are required using a counter
- While Loop (Condition-controlled)
- Loops until the condition is met/changes
- Better for user interfaces
- Loops until the condition is met/changes
- Repetition of a process
- For Counter (Counter-controlled)
- Operators
- Represents the operations that
are performed on the data
- Arithmetic Operators
- + - Addition
- - -
Subtraction
- * -
Multiplication
- / -
Division
- MOD - Modulus (Remainder) e.g.12 MOD 5 = 2
- DIV - Ouotient e.g. 17 DIV 5 = 3
- ^ - Exponentiation (To the power of)
- + - Addition
- Comparison Operators
- == - Equal to
- != - Not equal to
- < - Less than
- > - Greater than
- <= - Less than or equal to
- >= - Greater than or equal to
- == - Equal to
- Logical Operators (Only
used in Booleans)
- AND - Two conditions must be met
for the statement to be true
- OR - At least one condition must be
met for the statement to be true
- NOT - Inverts the results e.g. NOT(A and B) will
only be false when both A and B are true
- AND - Two conditions must be met
for the statement to be true
- String Operators
- .upper - UPPERCASE
- .lower - lowercase
- .length - Number of characters
in a string (including spaces)
- .substring (x,y) - Part of a string
- .upper - UPPERCASE
- Represents the operations that
are performed on the data
- Sequencing
- Allows a programmer to solve complex
tasks through a number of simple steps
- Benefits
- Each line follows the next
- Create simple programs very quickly
- Easy to follow for a small program
- Fundamental prinicipal of a prgram
- Starts at the top, finishes at the bottom
- Starts at the top, finishes at the bottom
- Each line follows the next
- Disadvantages
- Not at all efficient
- Becomes very difficult to
follow with large problems
- Extremely hard to maintain
- Not at all efficient
- Allows a programmer to solve complex
tasks through a number of simple steps
- SQL (Standard Query Language)
- Progranmming languague used to work with databases
- Can be run from a special window in a database package
- SELECT - SQL Keyword
- Accomplishes searching and reading simultaneously,
separates keywords from names and criteria
- Nested SELECT
- Multi-stage filtering e.g. finding all pupils in a set with the first
select and then just retrieve those who get over 80 in results
- Particularly useful in multi-table databases
- Multi-stage filtering e.g. finding all pupils in a set with the first
select and then just retrieve those who get over 80 in results
- Accomplishes searching and reading simultaneously,
separates keywords from names and criteria
- Progranmming languague used to work with databases
- Arrays
- An ordered collection of related data where each element
is accessible by a number, known as an index
- Advantages
- Good for ease of iterating through an array - allows us to
manipulate multiple times of data with very few lines of
code,replacing may separate variables
- Non-sequential nature - can jump between non-neighbouring elements
instantly without having to browse through the whole array
- Good for ease of iterating through an array - allows us to
manipulate multiple times of data with very few lines of
code,replacing may separate variables
- Advantages
- Usually have fixed sizes and occupy a
fixed (static) amount of memory
- Begins with 0
- An ordered collection of related data where each element
is accessible by a number, known as an index
- Sub Programs
- Can be used to save time and simplify the code. Main
types of sub programs are procedures and functions
- When you want your program to repeat in different places, you
only need to call the name of the subprogram, saving time &
simplifying the code by avoiding repetition of code
- Procedures are sets of instructions stored under one name
(identifier) e.g. Prodecure name () -> 'Coding' -> End Prodecure
- Functions are similar to procedures but
always return a value to the main program
- Can be used to save time and simplify the code. Main
types of sub programs are procedures and functions
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