Homework 7 Circuit simulator

CS 211 Homework 7
Circuit simulator

Introduction
You have to write a circuit simulator. One of the inputs to your program will be a circuit
description file that will describe a circuit using various directives. Your program will print
the output of the circuit for all possible input values.
Circuit Description Directives
The input variables used in the circuit are provided using the INPUTVAR directive. The
INPUTVAR directive is followed by the number of input variables and the names of the input
variables. All the input variables will be named with capitalized identifiers. An identifier
consists of at least one character (A-Z) followed by a series of zero or many characters
(A-Z) or digits (0-9). For example, some identifiers are IN1, IN2, and IN3. An example
specification of the inputs for a circuit with three input variables: IN1, IN2, IN3 is as
follows:
INPUTVAR 3 IN1 IN2 IN3
The outputs produced by the circuit is specified using the OUTPUTVAR directive. The
OUTPUTVAR directive is followed by the number of outputs and the names of the outputs.
An example specification of the circuit with output OUT1 is as follows:
OUTPUTVAR 1 OUT1
The circuits used in this assignment will be built using the following building blocks:
NOT, AND, OR, NAND, NOR, and XOR.
The building blocks can produce temporary variables as outputs, and can use either
the input variables or temporary variables as input. Output variables will never be used
as inputs in a building block.
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All the temporary variables will also be named with lower case identifiers (i.e., temp1,
temp2, temp3, . . . ).
The specification of each building block is as follows, where · denotes logical AND, +
logical OR, and ⊕ XOR:
Block Arguments Semantics
NOT IN1 OUT1 OUT1 = IN1
AND IN1 IN2 OUT1 OUT1 = IN1 · IN2
OR IN1 IN2 OUT1 OUT1 = IN1 + IN2
NAND IN1 IN2 OUT1 OUT1 = IN1 · IN2
NOR IN1 IN2 OUT1 OUT1 = IN1 + IN2
XOR IN1 IN2 OUT1 OUT1 = IN1 ⊕ IN2
Describing Circuits using the Directives
It is possible to describe any combinational circuit using the above set of directives. For
example, the circuit OUT1 = IN1 · IN2 + IN1 · IN3 can be described as follows:
INPUTVAR 3 IN1 IN2 IN3
OUTPUTVAR 1 OUT1
AND IN1 IN2 temp1
AND IN1 IN3 temp2
OR temp1 temp2 OUT1
Note that OUT1 is the output variable. IN1, IN2, and IN3 are input variables. temp1
and temp2 are temporary variables.
You can assume:
• The circuit descriptions given will be sorted.
– The first line gives the input variable(s).
– The second line gives the output variable(s).
– Every temporary variable occurs as an output variable before occurring as an
input variable.
• A temporary variable can be an output variable in at most one directive.
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Example Execution
Suppose our input has this description for the circuit OUT1 = IN1 · IN2 + IN1 · IN3:
INPUTVAR 3 IN1 IN2 IN3
OUTPUTVAR 1 OUT1
AND IN1 IN2 temp1
AND IN1 IN3 temp2
OR temp1 temp2 OUT1
Then your program should take the circuit description file as an argument and produce
the following output:
$ ./first circuit.txt
0 0 0 0
0 0 1 0
0 1 0 0
0 1 1 0
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 1
The output of the first three columns are the input variables IN1, IN2, and IN3 respectively
(as they iterate through all possible values). And the last column denotes the output
variable OUT1.
The printed values of the input and output variables should be space separated and be
in the same order (left to right) as listed in the INPUTVAR and OUTPUTVAR directive.
The order of the lines of input (top to bottom) should match the normal numeric order
when counting in binary.
Submission
Please submit a tar file named hw7.tar on Canvas that contains a hw7 directory. The hw7
directory in your tar file should contain the Makefile and your source code:
hw7
Makefile
first.c
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