CMPE13 Cyrus Bazeghi Hands on with Functions and IO

CMPE13 Program Inputs How do you pass information into your program? Use arguments in main() int main(int argc, char * argv[]) The names argc and argv are usually used for the parameters, but a programmer could use different names. 2

CMPE13 Program Inputs The command words can be accessed as argv[0] through argv[argc - 1]. The program name is the first word on the command line, which is argv[0]. The command-line arguments are argv[1] through argv[argc - 1]. argc holds how many arguments are passed 3

CMPE13 Simple Example #include int main(int argc, char * argv[]) { int i; printf ("You entered %d words\n",argc); for (i = 1; i < argc; i++) printf("%s ", argv[i]); printf("\n"); } 4 Now lets use it

CMPE13 File IO review We have discussed fopen, fclose, fprintf, & fscanf Example: –Look at the file_io.c example 5

CMPE13 More File IO To do more interesting things, need to more fine toothed control… fgetc() – Reads one character from a file fputc() – Writes one character from a file Example: my_cat.c 6

CMPE13 Basic Database Get the file “database.txt” from the class website in the Handouts and Links section Write a simple function that will read the elements out of the database and add them to a linked list that you dynamically create –You will need to make a structure to hold them –You will need a function to add a node to the linked list Now write 2 functions, one to add a node, one to delete, the add should prompt the user for the fields, the delete should ask for the ID or name Write a final function that will save the database back to the file

CMPE13 Caesar Cipher Algorithm 8 Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet.encryptionsubstitution cipherplaintextalphabet

CMPE13 Activity Write two functions, one called Caesar_Encrypt() the other called Caesar_Decrypt(). The Caesar_Encrypt should take 2 inputs, a string of characters and a key. The function should shift the characters by the key and account for “roll-around” at the end of the alphabet. The Caesar_Decrypt() should take the same types of input as the Caesar_Encrypt() function but reverse the process. Test the above with some character arrays. Put the functions in a file called crypto.c and make a header called crypto.h Now uses these to read in a file of text and produce a new file with the extension “.enc” 9 Part 1: Part 2: