2.2 Computing - Khang Duong

2.2 Computing - Khang Duong

1. A variable is a value that can change, depending on information passed to the program

2. Constants are values that don’t change as the program runs.

3. Sequencing allows a programmer to solve complex tasks through a number of simple steps.

   • To be able to break a complex task into a sequence of simple steps which would each require one line of pseudocode or a flowchart.
     • BENEFITS
       • Each line follows the next Create simple programs very quickly Easy to follow for a small program Fundamental principal of a program - Starts at the top, finishes at the bottom
     • NEGATIVES
       • Not at all efficient Becomes very difficult to follow with large programs Extremely hard to maintain

4. Selection 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.

   • There is no limit on how many selection statements we can nest.
   • The “outside” selection is the pre-condition, while the “inside” selection is the condition.
   • Efficiency in reducing the number of lines of code we would run We can’t evaluate a condition if some pre-condition is not met. We would need two selection statements, one inside the other.
   • We need programs to make decisions based on a set of criteria or condition.

5. Loops are called iteration because they run through or “iterate” through multiple similar items of data.

   • FOR counter (counter controlled) is when the loop for when we know in advance how many times we want to loop back to the start, so we keep count and check against the number of repetitions (iterations) that are required, using a counter.
   • WHILE (Condition-controlled) is when loops evaluate a Boolean condition every time they run (either in the beginning or the end of an iteration) and if it is true – they carry on, otherwise, the loop stops. Conditional loops are used for validation. Conditional loops are also good for searching.

6. We would like the data generated by a program to continue which means to stay stored somewhere for future use, this is known as Data Persistence. This can be done with text files, binary files, databases and browser cookies

   • Data stored in text files is meant to assume many forms and types once loaded into a program – but in the file it is always stored as a string (unless it’s a binary file which we don’t cover).

7. SQL stands for Standard Query Language, a popular human-readable programming language that is used to work with databases.

   • These databases are not stored in text files or CSV files but in binary proprietary formats

8. Nested select refers to multi-stage filtering.

   • This is useful in multi-table databases that don’t have proper relationships between the tables.

9. Arrays are made up of elements (items) holding related data. They are an ordered collection of related data where each element is accessible by a number, known as an index. Arrays usually have fixed sizes and occupy a fixed (static) amount of memory.

   • Every item in an array has an index
     • Some arrays can be two-dimensional or nested. To write or read an item, we provide its row first and its column.

10. Casting is changing an entity from one data type to another

11. OPERATORS

    • ADDITION = +
    • DIVISION = /
    • MULTIPLICATION = *
    • SUBTRACTION = -
    • MODULUS = MOD
    • QUOTIENT = DIV
    • EXPONENTIATION = ^
    • BOOLEAN
      • AND, OR, NOT, larger, smaller, equal, not equal
    • Boolean - True or false
      • String - any text not calculated