Text and binary

• Text files


  Sequence of characters that can be read by humans
• Character encoding


  Usually Unicode, but other formats can be used
• Opening a text file in a text editor


  1. Text editor software takes into account control characters

  2. Control characters are replaced with a different representation or acted on

  3. Text is then displayed
• Control characters


  Special characters read and interpreted by the editor
• Newline character


  • ASCII code 10, Unicode U+000A, often typed as \n
  • Backslash is an escape character, defines an escape sequence
• When the text editor reads the newline character, it is removed and any text following it is placed on a new line
• Understanding control characters is important as they can cause issues when working with text files
• CSV (Comma-Separated Values)


  • Type of text file widely supported by many programs
  • Useful format for moving data between applications
• CSV file


  • Uses a character set like ASCII or Unicode
  • Consists of records (typically one per line) divided into fields separated by delimiters
  • Has the same sequence of fields for every record
  • File name extension is generally .csv
• CSV files may have field names encoded in the first line
• When importing a CSV file, you are usually asked if there is a header line and what character has been used as the delimiter
• Contents of shopping.csv


  • Item, Description, Qty
  • Rice, Organic, 1kg
  • Milk, Skimmed, 2.27l
  • Eggs, Free-range, 60
  • Sugar, Brown, 500g
• All data on a computer is stored in binary sequences of 1s and 0s
• Text files


  Binary codes represent characters, which can be displayed in text editors
• Binary files


  • Hold information that is not character based, such as sound or image data
  • Encoded in a form that can be directly manipulated by a computer program
• Most computer files are binary rather than text files, as humans rarely need to read the raw file data
• File headers


  Tell the computer what kind of data it is looking at, especially important in program binary files
• Program binary file header

  • Prefix 'MZ' - initials of the programmer who invented the format
• Bitmapped graphic files


  • Images represented as a collection of pixels, each with an RGB colour code
  • Metadata also included in image files, such as dimensions and creation date
• Sound files


  • Analogue signal converted to binary by sampling at fixed intervals
  • Data points stored as binary numbers, reversed to recreate the sound wave
• Program files


  • Start as text files with programming language instructions
  • Compiled into machine executable binary format before being run
• Software companies are often reluctant to document and share the exact format of their binary files due to concerns about cybercrime and reverse-engineering
• The binary is processed by the program associated with it, and is translated back into the instructions and resources that the program needs