CS120 Day02: Execution Environment & gdb
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GDB ========================================

See James' notes and example files on bitbucket for using gdb!

- C "features"
    - obscure code
    - illicit hacking
    - system level programming
    - really efficient memory usage
    - shoot yourself in the foot

- different language versions evolved over time
- different implementations (compilers) based on platform/hardware

DATA TYPES ===============================
- primitive data types 
    - not as strongly typed as Java
    - exact sizes of each are implementation defined! (platform dependent)
    - char, short, int (default), long, float, double, long double
    - unsigned qualifier can apply to any (signed is default)
    - const qualifier (final in Java)

- integer constants
    - decimals (base 10)
       - int: 13, 23, -14, etc. 
       - long: 13L, -14l, etc. 
    - octal (base 8) - precede value with 0
       - digits range from 0 to 7
       - 032
    - hexadecimal (base 16) - precede value with 0x
       - digits range from 0 to 9 and a-f or A-F
       - 0x15, 0xA
	- binary (base 2) - precede value with 0b
       - digits are 0 and 1 only
       - 0b1000, 0b01101

- sizeof operator: returns integer # bytes of object
    sizeof (myarray), sizeof(anytype), sizeof varname
       # arrayelements = sizeof (myarray) / sizeof(arraytype)


- compiling into assembly and examining the code


OPERATIONS ==================================
if (num = 10)  // true
if (num == 10)

- bitwise operators
    num1 & num2 - bitwise and
    num1 | num2 - bitwise inclusive or
    num1 ^ num2 - bitwise exclusive or
    ~num1 - bitwise complement
    num << shiftbits - left shift of num by shiftbits places, pad 0 right
    num >> shiftbits - similar right shift, pad is system dependent

Usage/Examples: 
    - mask as application of &
    - set bits with |
	- see encrypt.c for examples

- built-in math functions
    - use #include <math.h>
    - may need to compile with gcc -lm option
    - generally take double arguments, return double values
    - eg: sqrt(x), pow(x,y), exp(x), log(x), ceil(x), floor(x), sin(x)

- output
    - void putchar(char);
    - puts("some string");
    - printf("format string", args...);
        - formats: (Appendix B)
            %i %d %f %c %s %n %ld %lf
            %o octal
            %x hex
        - field widths
            %cols.decf - eg. %.2f, %.6f
            right justified by default
            use %- to left justify 
            - and cols works for %d and %s also
- input
    - int getchar()
    - EOF predefined constant for end of file