Study guide: C Language Fundamentals

📋 Course Outline

1. C Language Origins and Uses
2. C Program Structure
3. Data Types and Variables
4. C Operators and Precedence
5. Programming Errors and Debugging
6. Compilation and Program Execution
7. C Storage Classes
8. C Language History

📖 1. C Language Origins and Uses

★ Must-know

• In 1972, Dennis Ritchie developed C at Bell Laboratories to write the UNIX operating system.

• C is an imperative, procedural, general-purpose programming language.

Further detail

• C is strongly associated with UNIX because it was developed to write that operating system.

• C is used to develop operating systems, databases, and embedded systems.

• The course describes C as structured, relatively easy to learn, efficient, suitable for low-level activities, and compilable on various computer platforms.

📖 2. C Program Structure

★ Must-know

• The six sections of a C program are:

  • documentation
  • preprocessor directives
  • definitions
  • global declarations
  • the main function
  • user-defined functions

• The preprocessor directive #include incorporates a specified file so its contents are compiled with the function being compiled.

• The main function is required in a C program and is the first function executed by the computer.

Further detail

• The documentation section gives an overview of a program, such as its name, date, description, and title, and does not interfere with the code.

• The header file stdio.h provides definitions for stdin, stdout, and stderr, while math.h is used for mathematical functions.

📌 Local declarations define variables inside a function or block, while global declarations are made in the program's global section.

• A return statement ends function execution and returns control to the calling function; it returns a value when the function's return type is not void.

💡 Memory Hook

A program moves from documentation and preprocessing to declarations, main, and user-defined functions.

📖 3. Data Types and Variables

🔑 Key Concepts & Definitions

• Data type: Specifies what kind of value a variable can store, the memory it requires, and the operations that can be performed on it.
• Variable: A named container for storing a data value.

★ Must-know

📌 C variable names must be unique, begin with a letter or underscore, and contain only letters, digits, or underscores; they are case-sensitive, cannot contain spaces or special characters, and cannot be reserved words.

Further detail

• C data types are classified as:

  • primitive
  • void
  • user-defined
  • derived

• Arithmetic primitive data types include integer and floating-point types, while void has no value and provides no result to its caller.

• The listed sizes are char 1 byte, float 4 bytes, and int 4 bytes.

• The course lists short int as 2 bytes with range -32,768 to 32,767 and format specifier %hd.

• The course lists float as 4 bytes with range 1.2E-38 to 3.4E+38 and format specifier %f.

💡 Memory Hook

Primitive types store values directly; derived types come from primitive or built-in types.

📖 4. C Operators and Precedence

★ Must-know

• C operators are grouped as:
  • arithmetic
  • relational
  • logical
  • bitwise
  • assignment
  • miscellaneous

📌 Relational operators compare values, while logical operators combine or reverse logical conditions.

• Operator precedence determines how an expression is grouped and evaluated, with higher-precedence operators evaluated first.

Further detail

• Arithmetic operators include:

  • addition
  • subtraction
  • multiplication
  • division
  • modulus
  • increment
  • decrement

• Bitwise operators act on individual bits; for example, with A = 60 and B = 13, A & B = 12, A | B = 61, and A ^ B = 49.

• The sizeof operator returns the size of a variable, the unary & operator returns its address, and the unary * operator dereferences a pointer to a variable.

• In x = 7 + 3 * 2, multiplication precedes addition, so x is assigned 13 rather than 20.

📖 5. Programming Errors and Debugging

🔑 Key Concepts & Definitions

• Debugging: The process of removing bugs or faults from a program.

★ Must-know

• The five listed types of C programming errors are:
  • syntax
  • run-time
  • linker
  • logical
  • semantic

📌 Syntax errors violate language syntax and are detected during compilation, whereas run-time errors occur during execution after successful compilation.

Further detail

• Division by zero is a common cause of a run-time error.

📌 A linker error prevents creation of the executable, while a logical error produces incorrect output despite the program being error-free in the compiler's sense.

• Semantic errors include:
  • using an uninitialized variable
  • incompatible types
  • invalid expressions
  • an array index out of bounds

📖 6. Compilation and Program Execution

📝 Essential Points

• A C compiler converts a program into machine-readable object files, and a linker combines object files into a single executable file.

📖 7. C Storage Classes

★ Must-know

• The four storage classes in C are:

  • auto
  • register
  • static
  • extern

• A static local variable retains its value between function calls and exists for the lifetime of the program.

📌 The extern storage class refers to a global variable or function defined elsewhere; an extern variable declaration cannot initialize the variable.

Further detail

• The auto storage class is the default for local variables and can be used only within functions.

📌 The register storage class suggests storing a local variable in a register, but its actual use depends on hardware and implementation restrictions.

• Applying static to a global variable restricts its scope to the file in which it is declared.

💡 Memory Hook

Static locals persist across calls, while extern refers to a global defined elsewhere.

📖 8. C Language History

📝 Essential Points

• In 1989, ANSI formalized the C language. - ANSI (American National Standard Institute), 1988

• C succeeded B and inherited features from B and BCPL.

• The listed languages developed before C are ALGOL (1960), BCPL (1967), B (1970), Traditional C (1972), K&R C (1978), ANSI C (1989), ANSI/ISO C (1990), and C99 (1999).

• The listed developers or committees are:

  • the International Group for ALGOL
  • Martin Richards for BCPL
  • Ken Thompson for B
  • Dennis Ritchie for Traditional C
  • Kernighan and Ritchie for K&R C
  • the ANSI Committee for ANSI C
  • the ISO Committee for ANSI/ISO C
  • the Standardization Committee for C99