CHAPTER 2 -----Reapresenting and Manipulating Information(1)

The familiar decimal, or base-10, representation has been in use for over 1000 years, having been developed in India, improved by Arab mathematicians in the 12th century, and brought to the West in the 13th century by the Italian mathematician Leonardo Pisano (c. 1170 – c. 1250), better known as Fibonacci(斐波那契，斐波那契数列).

 The evolution of the C programing language :The ISO take over responsibility for standardizing the C language ANSI C——>ISO C90(the same as ANSI C，sometimes called c89)——>ISO C99——>ISO C11

The GNU Complier Collection(gcc) can compiler programs accroding to the conventions of several different versions of the C language,based on different command line options.

For example, to compile program prog.c according to ISO C11,we could give the command line:

linux> gcc -std=c11 prog.c

 

2.1 Information Storage

most computers use blocks of eight bits,or bytes,as the smallest addressable unit of memory.A machine-level program views memory as  a very large array of bytes,referred to as virtual memory.

Each byte of memory is identified by a unique number,known as its address,and the set of all possible addresses is knowns as the virtual address space(虚拟地址空间).