![]() ![]() One can take advantage of this by writing instructions into mailboxes that are meant to be interpreted as code, to create self-modifying code. ![]() Care therefore needs to be taken to stop the Program Counter from reaching a memory address containing data - or the Little Man will attempt to treat it as an instruction. ![]() The latter is achieved by setting the Program Counter to a non-sequential memory address if a particular condition is met (typically the value stored in the accumulator being zero or positive).Īs specified by the von Neumann architecture, any mailbox (signifying a unique memory location) can contain either an instruction or data. Branch instructions allow iteration (loops) and conditional programming structures to be incorporated into a program. This Program Counter is normally incremented by 1 after each instruction is executed, allowing the Little Man to work through a program sequentially. The Program Counter holds the address of the next instruction the Little Man will carry out. In the center of the room, there is a work area containing a simple two function (addition and subtraction) calculator known as the Accumulator and a resettable counter known as the Program Counter. Furthermore, there are two mailboxes at the other end labeled INBOX and OUTBOX which are used for receiving and outputting data. At one end of the room, there are 100 mailboxes ( memory), numbered 0 to 99, that can each contain a 3 digit instruction or data (ranging from 000 to 999). The LMC model is based on the concept of a little man shut in a closed mail room (analogous to a computer in this scenario). ![]() It can be programmed in machine code (albeit in decimal rather than binary) or assembly code. The LMC is generally used to teach students, because it models a simple von Neumann architecture computer-which has all of the basic features of a modern computer. The Little Man Computer ( LMC) is an instructional model of a computer, created by Dr. ![]()
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