User types hello figure 15 reading the hello command

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Unformatted text preview: acters hello at the keyboard, the shell program reads each one into a register, and then stores it in memory, as shown in Figure 1.5. CPU register file PC ALU system bus memory bus main "hello" memory Memory Interface I/O bridge I/O bus USB controller mouse keyboard graphics adapter display disk disk controller Expansion slots for other devices such as network adapters. user types "hello" Figure 1.5: Reading the hello command from the keyboard. When we hit the enter key on the keyboard, the shell knows that we have finished typing the command. The shell then loads the executable hello file by executing a sequence of instructions that copies the code and data in the hello object file from disk to main memory. The data include the string of characters ”hello, world\n” that will eventually be printed out. Using a technique known as direct memory access (DMA) (discussed in Chapter 6), the data travels directly from disk to main memory, without passing through the processor. This step is shown in Figure 1.6. Once the code and data in the hello object file are loaded into memory, the process...
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This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.

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