Assignment 2: Strings, File IO, and command-line arguments

CSE109 
1
Systems Software
Assignment 2: Strings, File IO, and command-line arguments
Assignment Objectives
Students should demonstrate the following abilities:
1. Access text files for reading and writing from C programs
2. Use C string library functions to manipulate text
3. Pass command-line arguments to C programs
Assignment
A finite state machine (FSM) consists of a set of states, a set of transitions, and inputs/outputs.
It is used to model the behavior of machines or programs where the current state is determined
by the previous state and the values of the inputs. In the FSM below, the ovals represent the
states and the connections between the ovals represent the transition from one state to
another. The labels (text) over the transitions represent the input value that triggers the
transition. The FSM shows how an input text is processed to identify data items as identifier or
number. Such a machine can be used by a lexical analyzer, a piece of software that is part of a
compiler, to find the list of symbols used in a C program for example.
CSE109 Lehigh University Summer 2020
2
The FSM starts at the state START and will remain in the same state as long as the input
character is a space (blank or new line). The machine will transit from START to the state
BUILDING_NUMBER when the input character is a digit. It will remain in the same state as long
as the next character is a digit and will transit to the state NUMBER when a space is read. The
state NUMBER means that a data item of type number has been read and the machine will
transit to the state START to start the identification of a new data item. In the same way, you
can describe the behavior of the machine for the other states.
Write a program that uses an enumerated type to represent the names of the states. Your
program should process an input file and identify each data item as identifier, keyword, or
number. A keyword is an identifier that is found in the list of keywords. The list of keywords in C
language is provided at the end this assignment for your reference.
Here is a sample input and output of your program:
Input:
include
int main
int money 220 fifty 0 twenty 0 ten 0
printf
 money get_input
find_num_bills money fifty twenty ten
Output:
include - identifer
int - keyword
main - identifer
int - keyword
money – identifier
220 - number
fifty – identifier
0 - number
twenty – identifier
0 - number
ten – identifier
0 - number
printf - identifer
money - identifer
get_input - identifer
find_num_bills - identifer
money - identifer
fifty - identifer
twenty - identifer
ten – identifier
Number of identifiers: 14
Number of keywords: 2
Number of numbers: 4
CSE109 Lehigh University Summer 2020
3
Define a function transition that accepts two inputs, the current state of the state machine
and the current input character and returns the value of the next state of the machine. The
method should implement the behavior of the FSM as shown in the diagram above. The main
method calls transition for each character read from the input file to update the current
state with the state returned by transition. Below is a code snippet from the main function
to show you how to use the method transition.
typedef enum{ START, IDENTIFIER, NUMBER,
 BUILDING_IDENTIFIER, BUILDING_NUMBER
} state;
state current_state = START;
char current_char = read one character from the input file
while(current_char != EOF){
 current_state = transition(current_state, current_char);
 if(current_state == IDENTIFIER){
 check if the identifier is a keyword
 display the data item with the word identifier or keyword
 current_state = START;// move to new data item
 }
 else if (current_state == NUMBER){
 display the data item with the word number
 current_state = START;
 }
 current_char = read the next character from the input file
}
Include the header file <ctype.h> to use the library functions such as isdigit(ch),
isalpha(ch), and isspace(ch)that return 1 if their character argument ch is a digit, a
letter or a space (‘ ‘ or ‘\n’) respectively.
Save your C program in a file named symbol_analyzer.c . Your program should accept
one command-line argument that is the name of the input file. Test your program using the
input file sample.txt provided with this assignment. Your program should display the list of
identifiers, keywords, and numbers in addition to the following statistics for sample.txt.
Number of identifiers: 54
Number of keywords: 19
Number of numbers: 11
Submit the file symbol_analyzer.c on courseSite.
List of C language keywords:
auto break case char const continue
default do double else enum extern
float for goto if int long
register return short signed sizeof static
struct switch typedef union unsigned void
volatile while