Computers as Components, 2nd Edition

2.2 ARM Processor 61

2.2.2 Data Operations

Arithmetic and logical operations in C are performed in variables. Variables are

implemented as memory locations. Therefore, to be able to write instructions to

perform C expressions and assignments, we must consider both arithmetic and

logical instructions as well as instructions for reading and wr iting memory.

Figure 2.7 shows a sample fragment of C code with data declarations and several

assignment statements. The varia bles a, b, c, x, y, and z all become data locations

in memory. In most cases data are kept relatively separate from instructions in the

program’s memory image.

In the ARM processor, arithmetic ...