2.2 notes isaac

2.2 notes isaac

1. Some key terms

   • A variable is a memory location that changes throughout the program
   • A constant is a memory location that is fixed for the duration of the program
   • Assignment is labelling various inputs, constants and outputs with descriptive names
   • Information is stored in memory locations under descriptive names called "identifiers"
   • Concatenation is joining inputs/text variables together
   • Parameters are inputs coming from the console, from a file or from elsewhere in a modular program
   • iteration is when loops run similar types of data
   • A For Counter is a loop for when we know how many times we want something to loop so we use a counter
   • Stepping is when we skip or miss out when counting
   • A While Loop is used for validation and searching. Evaluates a boolean everytime they run
   • Nested Loops are used for iterating 2D arrays or generating complex sequencing
   • Data Persistence is when data is stored for future use
   • EOF (End of File) is a condition for the while loop to stop reading the file's lines
   • A Schema is a description of all possible element names and types
   • A Memory Leak is when you don't close a file not in use leading to wasted RAM space

2. Sequencing

   • Allows a programmer to solve complex tasks through a number of simple steps
   • Each line follows the next
   • Creates simple programs very quickly
   • Easy to follow for a small program
   • Fundamental principal of a program
   • Not efficient
   • Becomes very difficult to follow with large programs
   • Hard to maintain

3. Selection

   • Allows a computer to make decisions
   • Changes the flow of a program depending on a set conditions
   • Used for validation, calculation and making sense of a user's choice
   • Nested Selection
     • Only evaluates a condition if pre-conditions are met
     • There is no limit on how many selection statements we can nest
     • The outside selection is the pre-condition and the inside is the condition

4. An array up to 2D to a file

   • Iterate through an array using WRITELINE and writing elements to the file one by one
   • Serialise the array (convert to a string) using delimiters e.g. commas for columns and NewLines for rows in case of a 2D array
   • Uses numeric index not names
   • Array is an ordered collection of related data where each element is accessible by a number index

5. SQL (Standard Query Language)

   • A popular readable programming language
   • Used to work with databases stored in binary proprietary formats e.g. Oracle, MySQL
   • Purpose of SQL S-Search C-Create R-Read U-Update D-Delete