All computer programs use a combination of sequence, selection and iteration. Sequence is each and every line of code executed from top to bottom in order. Selection is when only certain lines of code are executed, dependent on a decision. Iteration is when lines of code are executed repeatedly as in a repeat loop.
A computer program must have the 7 following characteristics;
1. Correct – meets the software specification
2. Maintainable – changes can be effected easily and quickly
3. Reliable – free of design and coding bugs, correct for all specified outputs and it should work correctly every single time it is run
4. Readable – has design and code that can be easily understood by other programmers
5. Portable – may be adapted to run on computers other than that on which it was designed
6. Efficient – should not require processor time or storage resources disproportional to the scale of the program
7. Robust – should not fail no matter what input is entered by the user
There are 3 types of programming languages
1. Procedural – the programmer specifies the sequence of operation that is to be performed
2. Declarative – the programmer declares all of the facts and relationships at the outset
3. Event Driven – this allows the user to design the HCI with buttons, text fields etc. Blocks of code are triggered by events. Eg. push of a button, key press etc.
A high level programming language is similar to the English language and uses words such as IF, ELSE, REPEAT etc. But, a computer does not understand this as it understands machine code. Eg. Binary 01101011. A translator to translate high level language into a low level language for the computer to understand. There are 2 types of translators: compiler and interpreter. A compiler converts the whole block of code before the program as run where as an interpreter converts one line at a time.