CSE 1341: Topics Covered between Exams #1 and #2

CSE 1341: CS I (Fall, 1999)

Exam#1 review:
- distribution and interpretation
- some common problems:
  - B(I.1): language characteristics
  - I.2: truth table
  - I.3: "for" <=> "while", how to handle loop index increment
  - III.2: data type and loop count (also prompt)
  - IV: "switch" inside loop
- partial sample solutions to Exam#1: e1.c
functions: introduction and concept
- example functions in e1.c
- definition and body
- how to call it
- how to declare it
hw#7

questions about hw#7?
appearances of functions in programs
1. function declarations: function prototypes
  - result/return type and argument specifier
  - procedures in C (vs. in other languages)
2. function definitions: body
3. function calls:
  - parameter/argument passing
  - call handling and stack concept
library vs. user defined functions
function declarations compared to variable declaration
- declare before use
- default for functions (but not for variables in C)
- default for variable in other programming languages
functional structure in C:
- flat structure in C vs. other languages
- compare to variables: global, local, and within blocks
- scope rules (comparison)
why functions?
- divide-and-conquer for large problems/applications
- top-down design or stepwise refinement
- repeated operations
- cohesion within a block/sub-task
- coupling: where to cut things off
additional examples from Chapter 4
- no parameter/no return value: gameloop.c,
- one papameter/return value: iseven.c and c2ftable.c,
sharing information among functions
- parameters/arguments
- reference by value
- reference by address
- global variables: use with caution
- among different files
a look ahead: hw#8

exam#2 information
functions and algorithms: example programs
- factorials: fact.c, p.147 and p.152
- combinations: combine.c
- stepwise refinement example in Section 5.6,
  - and the final program calendar.c
- statistics and search (max, min, avg, match, selection, etc.)
algorithms: testing for primality
- basic ideas and implementation:
  - definition about factors
  - check the number of factors
  - implementation: primes1.c
- conformance and verification
- demonstrating correctness
- inspection (desk-checking) vs. formal verification vs. testing
- alternative algorithms and implementations
efficiency issues: primes2.c
- no need to get check multiple factors
- short-cut the loop once the answer is found
- even numbers?
- implementation: primes2.c
efficiency issues: primes3.c
- problem in primes2.c: specical case for 2
- efficiency in loops: sqrt function
- implementation: primes3.c
hw#8

questions about hw#8
algorithms: greatest common divisor
- brute-force: gcd.c
- efficiency issues
- a more efficient algorithm: euclid.c
numerical algorithms efficiency improvement
- make use of logical relations among items
- stop early: primes3.c;
  - stop when answer is found
  - stop before redundant situation appears
- jump over unnecessary steps: euclid.c;
- using bigger steps: primes3.c
- avoid un-necessary computation inside loop:
  - e.g. move sqrt() outside of the loop in primes3.c
algorithm comparison: recursion vs. iteration
- compare iterative Factorial (p.147 and p.604)
- recursive Factorial (p.605)
- efficiency comparison
- solution ideas: clarity comparison
- trade-off between the two.
functions and pointers
- an introduction to pointers
- sharing more than one data items
- the meaning of "&"
- the meaning of "*"
- xfer.c: example program for "transfer()"
looking ahead: graphics library and hw#9
for now: design on paper

partial solution to hw#8.
standard C vs. functional libraries and interfaces
- library functions: system and user defined
- interface: usage vs. implementation
- usability/function vs. portability/maintainability
- (standard) formatted I/O (text 15.5, pp.539-547)
- printf()
- "scanf()"
- use of header files
- abstraction, specification and prototype
- use in structured and object-oriented programming
- link to top-down design and stepwise refinement
graphics library
graphics.h
list of graphics library functions: p.227
what they do: specification (pp.228-230)
new: initializing package
examples: arc1.c, arc2.c, drawcirc.c, oneline.c
building your own tools: example programs
examples: drawcirc.c, drawbox.c, drawcbox.c
larger problem: e.g. "house.c" using stepwise refinement
top-down vs. bottom-up design
functions/tools from "house.c" that can be used for your hw#8:
- DrawCenteredCircle()
- DrawBox()
- DrawGrid()
hw#9
- design process and document
- program implementation/debugging/documentation
- demo

questions about hw#9?
principle of enumeration
- representing non-numerical information
- coding scheme
- character representation
- constant representation
enumerated types
- variables of enumerated types
- example: typedef enum {CSE, EE, ME} DeptInSEAS;
- associated values:
  - default: start with 0 and go up
  - over-write default values
  - individual definition, example
  - mixture, example
- example: ATM with enumerated types
  - atm.c
  - new data type: optionT
  - use in declarations/prototypes/parameters
  - associated values
advantage of enumerated types
- automatic coding by compilers
- simpler than named constants
- easy for reading/comprehension/modification
- debugging help
characters
- data type: char answer='y';
- example in primefactor.c
- single quote vs. double quote
- ASCII code (p.309)
- special characters (p.311)

computation with characters
- utilities based on ASCII code properties
- ctype.h library and interface
  - test: islower(ch), isupper(ch), isalpha(ch), isdigit(ch), isalnum(ch), ispunct(ch), isspace(ch)
  - convert: toupper(ch), tolower(ch)
- example in primefactor.c
- input: getchar()
- output: "%c" with printf()
sample programs
- sketch for "tolower()" (p.315)
- sketch for "IsVowel()/main()" (p.316)
- use of "getchar()":
  - lastchar.c
functions and algorithms with character type
strings as character arrays (later)
hw#10
review for Exam#2
- topics covered: on-line list
- focus on functions and algorithms
- use of library functions, particularly graphics.h and ctype.h

Prepared by Jeff Tian (tian@seas.smu.edu). Last update Nov. 3, 1999.