Assembly: Some background Why assembly? It is used to write 1.device drivers 2.Embedded systems 3.Real-time systems 4.Whenever there are significant speed or memory constraints

Assembly: Some background Assembly languages are specific to the machine architecture Although assembly supports data structures, these must be built and manipulated by the programmer with little sw support. Programs that require complex data structures or user interfaces are better written in a HLL.

VM concept Instead of thinking of languages (Java, assembly, and so on) you could imagine a “virtual machine” or a stack of such machines that sit on each other. VM0 can execute commands in L0. VM1 can execute commands in L1. If it is convenient we can execute commands directly on the hw at a given level. If not, we can translate/interpret from this level down to the next. VM(i) can’t be very different from VM(i-1) because translation between levels would be too difficult. If our highest level VM is not appropriate for the tasks we need to perform, we can build another level.

Actual machine (VM) levels High level language (level 5) Assembly (level 4)– large scale sw development is possible at this level. Mnemonics are used. Programs execute level 3 instructions or are translated down to level 2. These programs are typically translated (assembled) to machine language before execution. OpSys (level 3)—interactive commands to load, execute, display etc. This is translated down to the level 2 VM Instruction set architecture (level 2)– the first level at which users can write programs. Microarchitecture (level 1) Digital logic (level 0)

Data representation: Review Binary Unsigned Arithmetic in binary Ranges of representation per storage unit. Signed: Two’s complement Remarks on IEEE f-p standard. Conversion between bases 2, 4, 8, 16, 10.

Boolean operations : Review And, Or, Not, XOR Truth tables