Memory Map, Programming Language, and Windows Dr. Harold D. Camp IT February 2007

PC Memory PC computer memory is divided into segments, 64 kilobytes each (65,536 bytes, to be exact) Segment register in microprocessor indicates segment is to be accessed Segment 0 Contains memory pointers, device drivers, buffers, input/output ports, and other essential information required by the computer and its operating system Segment 0 contains 65,536 memory addresses Figures on next pages show how different portions of memory are allocated

PC Memory Figure 1 displays the entire contents of the 64K memory block that makes up Segment 0 Each pixel represents the contents of one memory location Each horizontal row in the display represents one 256 byte page

PC Memory The numerical values (in decimal) indicated by the different colors are shown in Figure 2 Blue areas indicated contain lots of zeros alternating with small numbers Memory set aside that has not yet been put to use 8 colored blocks located between H4100 and H8000 are probably associated with the 32 buffers that are indicated to be located there The areas with random color patterns relate to device drivers and hardware extensions, which are actually computer programs Areas of memory that are white are likely bits of unused memory that still contain the default hexadecimal value of FF (255 in decimal).

PC Memory Figures 3 and 4 Each colored line contains the mean value of one 256 byte page of memory Colored bands make it easier to see how different portions are allocated for different uses For instance, the blue-green and green blocks appear to be for data storage, since the buffers are located there Gray areas correspond to the areas where machine code is located The dotted lines in the gray zones that resulted from conversion from bitmap to gif format

PC Memory Figures 3 and 4 Each colored line contains the mean value of one 256 byte page of memory Colored bands make it easier to see how different portions are allocated for different uses For instance, the blue- green and green blocks appear to be for data storage, since the buffers are located there Gray areas correspond to the areas where machine code is located The dotted lines in the gray zones that resulted from conversion from bitmap to gif format

PC Memory

Memory Map

Machine Instructions/Programming Languages In Class Tutorial Be prepared to take notes

How do Operating Systems Work? system.htm Windows in particular

API (Application Programming Interface) html

So, How does API work?

Homework 4 Two page report on Intel Pentium instruction set architecture Instructions Addresses Memory Map