Introduction #

Writer prefer 1983 ANSI C (K&R 2nd). #

C was born for UNIX
- C is machine independent
- C is simple and concise (even though program with it is complicated)
Creator’s words
- C is a general-purpose programming language which features economy of expression, modern control flow and data structures, and a rich set of operators.
- C wears well as one’s experience with it grows.
- C is a relatively “low level” language.
standard library
- input output
- memory management
- string manipulation
- etc
What C provides
- data types
  - characters
  - integers
  - floating point numbers
  - and hierarchy of derived data types created with pointers, arrays, structures, and unions
- expressions are formed from operators and operands
  - any expression, including an assignment or a function call, cam be statement
- pointers provide for machine-independent address arithmetic
- control-flow
  - statement grouping
  - decision making (if-else)
  - selecting one of a set of possible cases (switch)
  - looping
    - with the termination test at the top (while, for)
    - with the termination test at the bottom (do)
    - early loop exit (break)
    - early loop skip (continue)
- Function
  - returns data type
  - may be called recursively
  - may exist in separated source files that are compiled separately
- Variables
  - declared autoatically
  - may be declared in block-structure
  - may be internal to function, external but known only within source files, and conditional compilation
- C is a relatively “low level” language
  - deals with characters, numbers, and addresses
  - there are no operations that manipulate an entire array or string
    - although structures may be copied as a unit
  - stirage allocation facility
    - static definition
    - stack discipline provided by the local variables of functions
    - there is no heap or garbage collection (?)
- Input / Output
  - C itself provides no input/output facilities
    - no READ, WRITE statement
    - no built-in file access methods
  - input/output provided by explicitly-called functions
- C supports only single-thread control flow (?)
  - tests, loops, grouping, subprograms
  - no multiprogramming