Algorithms and programming techniques

Algorithms and programming techniques

1. Algorithms

   • A set of step by step instructions to describe a process or a task.
   • Pseucode- a simple but structured way of writing algorithms. It is not a real programming language.
   • Flowcharts- a visual method of describing algorithms. Symbols are linked together using flow lines which show the sequence of steps to be taken.
   • Sequence- a set of instructions that must be followed in a specific order one after another.
   • Selection- the choice of what route to go through an algorithm. IF statements are used in python to represent this.
   • Iteration- repeating steps in a problem to make it more efficient.
     • 2 types of iteration- Counter controlled (for) and conditional controlled (while).
       • Conditional(while)- uses a condition as part of the decleration statement which is checked at the start of an iteration. Runs an infinite number of times.
       • Counter controlled (for)- uses a counter as part of the decleration statement. Runs a certain amount of times.

2. Data representation

   • Bit Nibble- 4 bits Byte- 8 bits Kilobyte- 1024 bytes Megabyte- 1024 kilobytes Gigabyte- 1024 megabytes Terabyte- 1024 gigabytes Petabyte- 1024 terabytes
   • character set- the character/symbols a computer understands or uses.
   • ASCII is used to represent keys/characters on a keyboard.
     • character set- 128 characters
     • ASCII only does english letters wheras unicode can do emojis, letters and other languages..
   • Analouge sound waves are used to capture sound which is then converted into a digital signal.
   • Images
     • Resolution- the number of pixels of the image is times by the number of pixels in width.
     • Colour depth- the amount of bits available for colours in an image.
     • Pixel- a single dot of colour in a digital bitmap image or on a computer screen.
     • To calculate number of colours available for a certain number of bits per pixel put 2 to the power of the number of bits per pixel. E.g 5 bits per pixel= 2 to the power of 5= 32

3. Programming techniques and errors

   • Variable- A named location in RAM (Memory). The value can change while the program is running.
     • Rules for variable names: -Must start with a letter -Can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9)-Case sensitive (AGE and age) are different things -cannot be a python keyword
   • Constant- A named location in memory (RAM). Once defined, the value cannot ever change while the program is running. Usually, the identifier is all uppercase.
   • Comments- lines of text which explain sections of code to the human reader. The computer ignores them. Benefits- easier for others to understand, explains what code does.
   • syntax error- an error which causes the program to stop running. An error in the rules of the programming language.
   • Logic error- an error that does not cause the program to crash but it produces an unexpected error.
   • casting- changing the data type.
   • IDLE (Integrated Development Learning Environment)- allows programmers to write, test and run their programmes.

4. Input, process, output

   • Input- a python function which accepts data from the user into the program.
   • output- the result of the processing is shown on the computer screen.
   • The user inputs information and then the computer processes and outputs data.