2.2.1 OCR AS Level Programming Techniques

2.2.1 OCR AS Level Programming Techniques

1. Programming Costructs

   • Sequence
     • Code is executed line-by-line, from top to bottom
   • Itteration
     • Code is executed while a condition is being me or for a certain amout of repeats.
       • Count controlled
         • When the itteration is repeated a set amount of times
           • FOR loops
       • Condition controlled
         • Itteration continued until a condition is met or stops being met
           • WHILE loops
   • Selection
     • When a certain block of code is executed if a certain condition is met
       • IF statements
       • Can be called branching

2. Global and Local Variales

   • Variables can be defined with either local or global scope
     • Where scope refers to the section of code in which the variable can be accessed
   • Local Variables
     • They have limited scope
       • Meaning they can only be accessed within the block of code in which they were defined
       • If it is defined within a subroutine it can only be accessed in that subroutine
         • Therefore, multiple local variables can exist with the same name without being affercted by or affecting each other
         • They are deleted once the subroutine has finished meaning they use less space
     • The use of local variables is considered good practice
       • Because it ensures subroutines are self-contained with no danger of variables being affected by code outside
   • Global Variables
     • Can be accessed across the whole program
       • Useful for values that need to be accessed throughout the whole program
     • Any variable declared in the main body of a program are automatically declared as global
     • Not recommended due to the risk of them being unintentionally overwritten and eddited
     • They use more space due to them not being deleted until the program terminated

3. Modularity, Functions and Procedures

   • Modularity
     • Modular programming is a programming technique used to split large complex tasks into smaller self-contained modules
       • Is essensial to making a problem easier to understand and approach
         • A modular design also makes it easier to:
           • Divide tasks between a team
           • Manage the development process
           • Simplify the process of testing and maintenance
             • As each component can be dealt with individually
               • This improves the reusability of components
                 • As once a module had been tested it can be reused with confidence
     • A popular technique used to modularise programs is the top-down approach
       • This is where the problem is continually broken down into sub-routines
         • Until each can be represented as an individual, self-contained, blackbox which performs a certain task
           • These modules form blocks of code called subroutines
             • Which can be either of
               • Functions
               • Procedures
       • This can also be called stepwise refinement
   • Procedures vs Functions
     • Functions and procedures are both named blocks of code that perform a specific task
     • Procedures dont have to return a value
       • Whereas functions have to return a value
     • Procedures can return multiple values
       • Functions have to return 1 single value
     • Functions usually use local variables
       • But procedures are typically given data as parameters
         • Parameters
           • Values passed into a function
           • When parameters are passed into a subroutine they can be passed by referance or by value
             • By value
               • When a parameter is passed by value it is treated like a local variable
                 • A copy of the value is passed into the subroutine and discarded at the end
                   • Therefore its value outside the subroutine is unaffected
             • By refrance
               • When a parameter is passed by reference the subroutine is given the address of the parameter
                 • Therefore the value of the parameter will be updated at the given address

4. Use of an IDE

   • An Integrated Development Environment or IDE
     • Is a program that provides a set of tools to make it easier for programmers to write, develop, and debug
   • Common features include
     • Stepping
       • This allows you to monitor the individual effect of a line of code
         • By executing a single line at a time
     • Variable watch
       • Lets a programmer observe how the contents of a variable change in real time
         • Sometimes used to pinpoint errors
     • Breakpoint
       • Allows users to set a point in the program where the program will stop
         • Could be condition based or at a specific line
     • Source Code Edditor
       • Aims to make the coding process easier by
         • Autocompleting words
         • Indenting
         • Highlighting syntax
         • Auto completing brackets
     • Debugging Tools
       • Some IDEs will provide systems to check for errors
         • With a guide as to where they likely occurred through line numbers and highlighting

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