PHY 107 – Programming For Science

History of C  Dennis Ritchie developed C from 1969 – 1973  Based upon B (& other) earlier languages  Since its creation, language grown organically  Tradition of adding features beyond standard as desired

History of C++  Bjarne Stroustrup created to add “objects”  Also included many other improvements to language  Name is inside joke: "++" increases value by 1 in C  Updated for quick growth  ISO standard adopted in 1998  Recently updated to C x

C Versus C++ C++ is designed to be as compatible with C as possible, thereby providing a smooth transition from C

C Versus C++ C++ C

C Versus C++ C

 Latest definition of C added most C++ features  Classes & objects excepted, these only found in C++  For this reason, also not a part of PHY 107  Differences now minimal and easily avoided  Once objects removed, C++ just “looser” C  Removes annoying restrictions that had been in C  Since makes life easier, often supported in C anyway

Case-Sensitivity  Example of computers being very literal  And language not helping by fixing what you say  main, Main, & MAiN treated as totally different  Case of the letters matters, not just the words  Might want difference; C won’t change Main to main  Can help prevent easy mistakes from swapping names  With just a little practice, becomes second nature

“Whitespace”  One (very small) way C/C++ actually helps you  Treats all whitespace equally – spaces, enters, & tabs  Whether 1 or – all will be ignored  Cannot use in symbol, whitespace splits words  Treats these as different “ : : ” and “ :: ”  Spaces between words needed, but not counted  Wecansplitwordsbutthecomputercannot

“Whitespace”  One (very small) way C/C++ actually helps you  Treats all whitespace equally – spaces, enters, & tabs  Whether 1 or – all will be ignored  Cannot use in symbol, whitespace splits words  Treats these as different “ : : ” and “ :: ”  Spaces between words needed, but not counted  Wecansplitwordsbutthecomputercannot

Your First C Program #include #include int main() { /* Hi, Mom. This is a comment that goes over 2 line. */ printf(“Hello world!”); return 0; // This comment goes to the line’s end }

#include Statements #include #include int main() { /* Hi, Mom. This is a comment that goes over 2 line. */ printf(“Hello world!”); return 0; // This comment goes to the line’s end }  Nearly every C file begins with these lines  May add more #include to include other files  Contents of included file usable as if it were here  Easy way to copy ideas across multiple files  Programs can use two types of #include statements  Include system file using #include  #include “ filename ” includes a file you wrote

Watch Me Pull a Rabbit #include #include int main() { /* Hi, Mom. This is a comment that goes over 2 line. */ printf(“Hello world!”); return 0; // This comment goes to the line’s end }  For now, automatically start each file with this line  Details are unimportant – consider it magic

Watch Me Pull a Rabbit #include #include int main() { /* Hi, Mom. This is a comment that goes over 2 line. */ printf(“Hello world!”); return 0; // This comment goes to the line’s end }  For now, automatically start each file with this line  Details are unimportant – consider it magic

Your First C Program #include #include int main() { /* Hi, Mom. This is a comment that goes over 2 line. */ printf(“Hello world!”); return 0; // This comment goes to the line’s end }

main Function #include #include int main() { /* Hi, Mom. This is a comment that goes over 2 line. */ printf(“Hello world!”); return 0; // This comment goes to the line’s end }  All C++ programs contain function called main  Tells computer where to start running program  Code inside the braces will be what is executed  For the moment, consider this more “magic”

main Function #include #include int main() { /* Hi, Mom. This is a comment that goes over 2 line. */ printf(“Hello world!”); return 0; // This comment goes to the line’s end }  All C++ programs contain function called main  Tells computer where to start running program  Code inside the braces will be what is executed  For the moment, consider this more “magic”

Comments  Vital  Vital for writing and maintaining any program  Not required to run program - only for human eyes  Computer simply ignores anything in a comment  Use to describe code in simple English  Sie konnen auch auf Deutsch schreiben  o U c%d wrte n txt msg  Should be used liberally  I add comments where cannot see what code does  Impossible to have too many comments, if readable

Comments in C/C++  Double slash comments continue to line’s end a = a – 4; // Hi, Mom! // This entire line is a comment!  /* … */ comments can be on one or more lines a = a - /* Hi, Mom! */ 4; /* This comment takes an entire line. */ /* This is a really long comment that * goes on to multiple lines. The stars on * lines 2 and on are optional, but * makes things easier to read. */

Your Turn  Work on activity in groups until 11:45  Each group will submit 1 copy at end  Professor chooses the copy; so must work together

For Next Lecture  Will have lab tomorrow, so bring flash drive  Have not done much, but we can start to see system  Read pages 34-37, 57-59, for Friday  What is a data type?  What are variables?  How do variables differ from numbers and letters?  Week #1 assignment on D2L & due Tuesday relies on tomorrow’s lab  This week different – relies on tomorrow’s lab