GCSE (9-1): Computer Science: AQA: String Operations

• String

  This data type stores a series of characters, e.g. "Zak", "MK44 5AB" or "123456789"
• LEN

  A function that determines how long a string is, i.e. the character count
• Character Code

  The numeric value of a character in a the character set. In ASCII, "A" is 65
• POSITION

  A function that returns the numeric location of a character within a larger string (counting from 0)
• Concatenation

  Joining two strings together, usually uses the + operator, for example fullname = firstname + lastname
• SUBSTRING

  A function in pseudo-code that returns part of a string when we pass it a starting position and length
• "Char"

  The string returned by this pseudo-code:SUBSTRING(0, 4, "Character")
• 6

  The value returned by this pseudo-code (assuming count starts at zero):POSITION("Character", "t")
• "Charlie"


  The result of the expression "Cha" + "rlie"
• STRING_TO_INT

  A casting function that changes a string to an integer, if the string contains only numeric characters
• STRING_TO_REAL

  A casting function that changes a string to a real number, if the string contains only numeric characters and a decimal point
• INT_TO_STRING

  A casting function that changes an integer to a string
• REAL_TO_STRING

  A casting function that changes a real number to a string
• Data type


  The kind of data a variable contains, it can be character, string, integer, real or boolean
• Character

  The data type of a single character e.g. "A" or "$"
• Casting

  Changing the data type using a function such as STRING_TO_INT() or REAL_TO_STRING
• STRING_TO_INT('12')


  This AQA standard pseudo-code expression uses a casting function to change a string to an integer and results in the integer value 12
• REAL_TO_STRING(12.8)

  This AQA standard pseudo-code expression uses a casting function to change a real to a string and results in the string value "12.8"
• STRING_TO_REAL('12.8')


  This AQA standard pseudo-code expression uses a casting function to change a string to a real and results in the real value 12.8