C Types

• Usual Types:     int, float, char


• Variations on Usual Types:     short int (short), long int (long), double


• Usual Operators:

  +, -, *, /, %,
  ==, !=, <, <=, >, >=

• Arrays:
  • Array definitions must specify type and size, e.g., int myArray[20];
  • Size is static
  • Array declarations (e.g., parameter declarations) just specify type, e.g., int myArray[]
  • Multi-dimensional arrays are arrays of arrays, e.g., int my2DArray[4][20];
  • Array indexing is actually syntactic sugar for pointer operations, e.g., myArray[i] == *(myArray + i)
    Array declarations are actually syntactic sugar for pointer declarations, e.g., int myArray[] == int * myArray


• Struct and Union:

      typedef struct tagName
      {
          char  c;
          int   i;
          float f;
          struct tagName * next;
      } Type1;
  
      typedef union tagName
      {
          char  c;
          int   i;
          float f;
          struct tagName * next;
      } Type2;
  



• Bit Flags:
  • Not an actual type, but there are bit-wise operators, e.g., <<, >>, &, |, ~


• What's missing?
  • bool, for one
  • But there are boolean expressions and boolean operators! ==, !=, &&, ||, !


• More about Pointers & Memory
  • What does it mean to say that C, C++, & Java support jagged but not rectangular arrays?

        int array2D_a[3][5];
        int array0[5] = { 1, 2, 3, 4, 5};
        int array1[7] = { 1, 2, 3, 4, 5, 6, 7};
        int array2[5] = { 1, 2, 3, 4, 5};
        int array2D_b[3];
        array2D_b[0] = array0;
        array2D_b[1] = array1;
        array2D_b[2] = array2;
        array2D_a[1][4] = 42;
        array2D_b[1][4] = 42;
        array2D_b[1][6] = 13;
        array2D_a[1][6] = 83;
    

  • What are dangling pointers, memory leaks, garbage collection?