The term location in Table 4.1 refers to whether memory is internal and exter-
nal to the computer. Internal memory is often equated with main memory. But there
are other forms of internal memory. The processor requires its own local memory, in
the form of registers (e.g., see Figure 2.3). Further, as we shall see, the control unit
portion of the processor may also require its own internal memory. We will defer
discussion of these latter two types of internal memory to later chapters. Cache is
another form of internal memory. External memory consists of peripheral storage
devices, such as disk and tape, that are accessible to the processor via I/O controllers.
An obvious characteristic of memory is its capacity. For internal memory, this is
typically expressed in terms of bytes (1byte = 8bits) or words. Common word lengths
are 8, 16, and 32 bits. External memory capacity is typically expressed in terms of bytes.
A related concept is the unit of transfer. For internal memory, the unit
of transfer is equal to the number of electrical lines into and out of the memory
The term location in Table 4.1 refers to whether memory is internal and exter-nal to the computer. Internal memory is often equated with main memory. But thereare other forms of internal memory. The processor requires its own local memory, inthe form of registers (e.g., see Figure 2.3). Further, as we shall see, the control unitportion of the processor may also require its own internal memory. We will deferdiscussion of these latter two types of internal memory to later chapters. Cache isanother form of internal memory. External memory consists of peripheral storagedevices, such as disk and tape, that are accessible to the processor via I/O controllers.An obvious characteristic of memory is its capacity. For internal memory, this istypically expressed in terms of bytes (1byte = 8bits) or words. Common word lengthsare 8, 16, and 32 bits. External memory capacity is typically expressed in terms of bytes.A related concept is the unit of transfer. For internal memory, the unitof transfer is equal to the number of electrical lines into and out of the memory
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