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lara31 [8.8K]
3 years ago
14

What bit position in an ascii code must be complemented to change the ascii letter represented from uppercase to lowercase and v

ice versa?
Computers and Technology
1 answer:
MariettaO [177]3 years ago
4 0
Flip bit position 5 to accomplish this. This maps to hex value 0x20, where the least significant bit is assumed to be at position 0.

Example: ascii "A" = 0x41, "a" = 0x61.  0x41 xor 0x61 = 0x20.

You would implement a flip function by XOR'ing the character value with 0x20.
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You are going to implement virtual memory for the LC-3 simulator so up to 32 LC-3 tasks can be active in the LC-3 simulator memory without corrupting each others data. To implement the virtual memory, we have routed all accesses to LC-3 memory through a get Mem Adr function that is the MMU for the LC-3 simulator. In essence, we now have a single LC-3 simulator with a single unified global memory array yet we provide multi-tasking in the simulator for up to 32 LC-3 programs running in their own private address space using virtual memory.

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The memory layout for the LC=3 simulator including the system (kernel) area that is always resident and non-paged (i.e., no virtual address translation).

The two figures try to illustrate the situation. The lower figure below demonstrates the use of the two level page table. The RPT resident in non-virtual memory is first referenced to get the address of the second level user page table or (UPT) for short. The right figure in purple and green illustrates the memory layout more precisely. Anything below the address 0x3000 is considered non-virtual. The address space is not paged. The memory in the region 0x2400 through 0x3000 is reserved for the RPTs for up to thirty-two LC-3 tasks. These tables are again always present in memory and are not paged. Accessing any RPT does not require any type of address translation.

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