week13 - home - clark science centerexercise • write a program that reads the ﬁle data.txt,...

mith College

Computer Science

Dominique Thiébaut dthiebaut@smith.edu

CSC231Week 13— Introduction to C

Fall 2019

Complete the code

shown here

Computer Science Dominique Thiebaut

getcopy C/decrementArray.c

Exercise

Complete the code

shown here

Solution

Exercise

• Write a C program that uses functions to find the largest integer in A. The result is passed back using a return statement.

Solutiongetcopy C/findMaxUsingFunctionSol.c

Exercise

• Write another program that does the same thing but the max is passed back by reference.

Solutiongetcopy C/findMaxUsingFunction2sol.c

Input/OutputIO

Input From User

(cont’d)

a.outEnter your name, please: MickeyEnter your age: 21Enter your version of pi: 3.14159Mickey is 21 years old, and thinks pi is 3.1415901184

Dynamic Variables

• Dynamic: think "new" in Java

• malloc() = Memore Allocation for new data structure

malloc()

OperatingSystem

malloc()

OperatingSystem

(void*) p

malloc()

OperatingSystem

(void*) p

malloc()

getcopy C/malloc1.c

Malloc

Exercise• Modify the previous program that computed the

max of an array, but this time you allocate the array dynamically, with numbers provided by the user.

Solution

getcopy C/findMaxUsingFunction3sol.c

sizeof()can be tricky…

sizeof ()

sizeof(A) = 20sizeof(A[0]) = 4sizeof(B) = 8sizeof(B[0]) = 4sizeof(p) = 8sizeof(*p) = 4sizeof(name) = 14strlen(name) = 13sizeof(a) = 4sizeof(x) = 4

sizeof ()

sizeof(A) = 20sizeof(A[0]) = 4sizeof(B) = 8sizeof(B[0]) = 4sizeof(p) = 8sizeof(*p) = 4sizeof(name) = 14strlen(name) = 13sizeof(a) = 4sizeof(x) = 4

Different!

sizeof ()

File IO

File I/O: Output

C/fileIOOutput.c

File I/O: Input

C/fileIOInput.c

File I/O: Reading Ints [~handout] cat fileOfInts.txt 41 2 34 5 67 8 910 11 12

File I/O: Reading Ints

C/fileIOReadNumbers.c

[~handout] gcc fileIOReadNumbers.c[~handout] a.out1, 2, 34, 5, 67, 8, 910, 11, 12

File I/O: Reading Ints

Exercise• Write a program that reads the file data.txt, which

has the number of ints it contains on the first line, then one int per line for the rest of the file. Your program must use a dynamic array to store the numbers, and find the max of the array, and print it.

Function Prototypes

and Multi-File Projects

Original

myfuncs.c

smallestLargestSum3.c

myfuncs.h

Summary• C has a lot in common with Java

• C programmers must know how to use memory (malloc, pointers)

• No garbage collector: free dynamic structures yourself!

• Explicitly pass arguments by value or by reference to functions

D. Thiebaut, Computer Science, Smith College

End of Video Lecturehttps://www.youtube.com/watch?v=LFpoUFIfV0M&a=youtu.be

Logistics and Update

• Video lecture for Monday's snow day + Quiz

• No office hours today

• Office hours tomorrow (12/5) 12-1 p.m.

• Homework extended to 12/5 11:55 p.m.

• Homework 11 (optional) released tomorrow morning

And now, something completely different…

Executablegcc addition.c

And now, something completely different…

Executablegcc addition.c

gcc -S -m32 -masm=intel addition.c

ReviewMalloc

Linked-Listsin C

Outline

• Linked Lists in C

• Structures in C

• Creating a Node

• Adding a Node

• Removing a Node

‘Alpha’

‘Zero’

‘Beta’

‘Apple’

"Alpha"

"Zero"

"Beta"

"Apple"

((void *)0)

"Alpha"

"Zero"

"Beta"

"Apple"

The Node in C"Alpha"

http://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#Structures

C Structs

• Early attempt at encapsulating data

• Members are accessed using the dot notation:

http://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#Structures

Struct Example

getcopy C/structExample.c

The Head of the List

That’s anempty list!

Displaying the List

"Alpha" "Zero" "Apple"

"Beta"

Creating the List

"Apple"

"Beta"

getcopy C/linkedListStrings.c

Exercise

• Add code to the linkedListStrings.c program that will remove all the nodes from the list, one by one (and free them).

• Make your code display the list after each deletion

Exercise

• Use functions for adding and removing nodes…

Main ProgramCalling

Functions

Solution

getcopy C/linkedListStrings2.c

We stopped herelast time!

week13 - home - clark science centerexercise • write a program that reads the ﬁle data.txt,...

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