Notes

• The definition refers to the place where the variable is created or assigned storage; declaration refers to places where the nature of the variable is stated but no storage is allocated.

Data Types

• Basic data types :
  • char: a single byte, capable of holding one character in the local character set
  • int: integer, typically reflecting the natural size of integers on the host machine
  • float: single-precision floating-point
  • double: double-precision floating-point
• There are also qualifiers that can be applied to these basic types:
  • short and long apply to integers. short and long should provide different lengths of integers. Usually, short is 16 bits long, int will be the natural size for a particular machine (32 or 16 bits), and longs are at least 32 bits. But always: long>int>short.
  • signed and unsigned can be applied to char or any integer. unsigned numbers are always positive or zero. Whether chars are signed or unsigned is machine-dependent, but printable character are always positive.
  • long double specifies extended-precision floating point.
• Mixing Types:
  1. If one thing in the expression is a floating type, convert the other things to that floating type.
  2. Otherwise, if both types are integer types, perform the integer promotions on each, then make the operand types as big as they need to be hold the common largest value. Sometimes this involves changing signed to unsigned.
• Conversion functions:
  • sprintf(): Convert a number to a string
  • strtol(): (String-to-long) family:
    • strtol(): String to long int
    • stroll(): String to long long int
    • strtoul(): String to unsigned long int
    • strtof(): String to float
    • strtod(): String to double
  • Atoi (ASCII-to-integer) family:
    • atoi(): String to int
    • atof(): String to float
    • atol(): String to long int
    • atoll(): String to long long int

Functions

• If a function takes no parameter use void: int foo(void)
• main() arguments:
  • argc: Argument count, including the program name.
  • argv: String of all the arguments. The last argument is a pointer to NULL

Structs

• Structs can be initialized:

  • Accessing every member:

    saturn.name = "Saturn SL/2";
    saturn.price = 15999.99;
    saturn.speed = 175;
    

  • With {}: struct car saturn = {"Saturn SL/2", 16000.99, 175};

  • With: struct car saturn = {.speed=172, .name="Saturn SL/2"};

• When to use arrow operator -> or .:
  • If you have a struct, use dot (.).
  • If you have a pointer to a struct, use arrow (->).

Typedef

• Typedef: Basically, you take an existing type and you make an alias for it with typedef.

  **typedef** int antelope; *// Make "antelope" an alias for "int"*
  

• The correct way to use typedef with structs is to define them as we rename them:

  typedef struct animal {
      char *name;
      int leg_count, speed;
  } animal;
  // From now on to use this struct we only need to:
  animal cat;
  

Strings

• Strings are arrays of chars
• Strings are terminated with NULL char( \\0)