simple C program

timer Asked: Sep 6th, 2017
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please see the attachments in order to know what are the requirements and what is the assignment about.

i uploaded two files; one is about the assignment and the other is notes teaching how to do this.

it is so easy.

thank you

ECE 102 Assignment #1 Getting Started with a Simple C Program /*This program computes the distance traveled by a satellite in one orbit given its altitude*/ #include #include /*printf, scanf definitions */ #define D 12730 /*earth diameter*/ #define pi 3.1415926 int main(void) { int altitude, /*distance in miles */ orbit; /*equivalent distance in km*/ /*Get the distance in miles*/ printf("Enter the altitude in kilometers> "); scanf_s("%d", &altitude); /*Convert the distance to kilometers*/ orbit = pi * (2 * altitude + D); /*Display the distance in kilometers*/ printf("The satellite travels %d kilometers in one orbit if the altitude is %d kilometers.\n", orbit, altitude); system("pause"); return 0; } /* */ 1. Enter the C program shown above. 2. At the top, add comments with your name, section number, current date, and the name of the assignment. You should do this for every computer program you write in this class. 3. Compile the program. Review the error messages to correct the errors, if any, in the program. If you have difficulty understanding the errors, or knowing how to correct them, ask the instructor or TA. 4. Run the program. Check the answer the program gives you with your correct answer. 5. Copy and Paste the results at the end of your program between /* and */. Save and compile again. 6. Load the final .c file only in the D2L Dropbox, under Assignment #1. Remember to name your file according to the naming convention: Lastname_FirstName_1. 7. Make sure you click on the submit button once the file is uploaded to D2L. The grader cannot see the file until you click on the submit button.
ECE102 Engineering Problem Solving What’s in a Program? Chapter 2 Simple C Programs • Basic C Program Structure • The basic steps of programming problems 1. Get input data #include < > 2. Check the validity of data #define 3. Perform computations int main ( ) 4. Display results { /*********************************************** * Header Comments ************************************************/ include files global declarations • The basic structure of a main program int main( ) { declarations; • The basic C syntax! executable statements; return 0; }/%end block of main%/ ECE102 } declare variables get input data calculation display results return 0; • Apply the five-step problem solving method 2-1 A Simple Program ECE102 2-2 Straight-line Distance Between Two Points /* This program computes the distance between two points */ #include #include #include int main(void) { /*declare and initialize variables */ double x1 = 1, y1 = 5, x2 = 4, y2 = 7; double side_1, side_2, distance; /* compute sides of a right triangle */ side_1 = x2 ‐ x1; side_2 = y2 ‐ y1; /*calculate the distance */ distance = sqrt(side_1*side_1 + side_2*side_2); /*print the distance */ printf("The distance between the two points is %5.2f \n", distance); system("pause"); return 0; } ECE102 2-3 ECE102 2-4 Pay Attention to Syntax!!! Comments • When learning a new language or a new concept in a language, remember to pay attention to the syntax – Syntax is the “grammar” of programming languages. • Used to document programs • Comments help people read programs, but are ignored by the compiler. • Review the example program and try to guess what things are the syntax – What is the syntax: special characters, order of things, – Remember to follow the syntax when writing your own programs • Use ; (semicolon) at the end of every command, • Well-conceived and wellplaced comments enhance the readability of the source code. • Syntax: – Identify where semicolon should not be used /* ------- */ (one line) /* -----------(multiple lines) -------------*/ /*----------------------------*/ /* This program computes the distance between two points */ #include #include #include int main(void) { /*declare and initialize variables */ double x1 = 1, y1 = 5, x2 = 4, y2 = 7; double side_1, side_2, distance; /* compute sides of a right triangle */ side_1 = x2 ‐ x1; side_2 = y2 ‐ y1; /*calculate the distance */ distance = sqrt(side_1*side_1 + side_2*side_2); /*print the distance */ printf("The distance between the two points is %5.2f \n", distance); system("pause"); return 0; } ECE102 2-5 ECE102 What to Comment on #include Preprocessor Directives • Initial comments (header comments) – – – – – • The preprocessor reads and modifies the source code before it is passed to the compiler. Describe the general purpose of the program List of inputs and outputs Author Date Copyright • C itself did not have easy input, output, math, and other routines built in. These functions are provided in standard libraries. • #include includes library files to give access to a library. #include #include • Comments within the program – Describe the meaning of the variables, if applicable – Functionality of blocks of lines • Math.h contains elementary math functions such as sin(x), cos(x), sqrt(x), pow(x,y), abs(x), … • Good programming style requires that comments be used throughout a program to improve the readability and to document the computations. ECE102 2-6 2-7 ECE102 2-8 The main Function Keywords (Reserved words) • Keywords are reserved words with special meaning to the C compiler • Syntax (grammar rules of a programming language) preprocessing directives int main (void ) { /*function body*/ declarations statements • Keywords cannot be used for any other purpose • They always mean what they are defined to mean in C • Improper use of keywords result in an error that prevents the program from compiling return 0; • Keywords are listed in Table 2.1 (typo: ints should be int) } • Braces { } mark the beginning and the end of the program. • Find the keywords in the sample program • Every C program has ONE and only one main function ECE102 int, double, return 2-9 ECE102 2-10 Computer Memory Data Type • Four basic types 01010001 • Terminology: 01001101 – Memory is divided into numbered locations called bytes. – A byte is a sequence of 8 bits. – A bit is a binary digit (0 or 1). – The location number associated with a byte is called the address. – A group of consecutive bytes is used for storing the binary representation of a data item, such as a number or a character. ECE102 2-11 type size description char 1 byte character int 2 or 4 bytes whole number float 4 bytes floating point number (6 digit precision) double 8 bytes • Examples: double precision floating point number (15 digit precision) data type int -1 data type double -1.0 ECE102 435 4.35 +5 32767 +5.9e4 0.3e-5 2-12 Numeric Data Type Example Data-Type Limits • Compiler dependent • In Visual Studio 2013 Type Name Bytes Other Names Range of Values int 4 signed –2,147,483,648 to 2,147,483,647 char 1 none –128 to 127 by default 0 to 255 when compiled by using /J short 2 unsigned short 2 short int, signed short –32,768 to 32,767 int unsigned short int 0 to 65,535 long 4 long int, signed long int –2,147,483,648 to 2,147,483,647 unsigned long float 4 unsigned long int 0 to 4,294,967,295 4 none 3.4E +/- 38 (7 digits) double 8 none 1.7E +/- 308 (15 digits) long double same as none double ECE102 2-13 Same as double ECE102 Example Data-Type Limits 2-14 Scientific Notation • Compact notation used for very large or very small numbers • Numbers are stored as mantissa and exponential form 234.56 = 2.3456 X 102 2.3456e2 exponent -0.00045= - 4.5 X 10-4 = - 4.5e-4 • Exercise: 1.03e-5 = -50000 = -3.552e6 = 10,000,028 = • Precision: the number of digits in the decimal portion of the mantissa ECE102 2-15 ECE102 2-16 Data Type char • Examples: ‘A’ ‘z’ ‘*’ Variables • We use variables to represent values in C programs. ‘9’ • Stores ASCII values • Variables are memory locations that are assigned a name or identifier. • Interprets the number stored in that variable as a character rather than a number – Character ‘3’ is different from the integer 3. • The identifier or variable name is used to reference the value of the variable or, what is stored in the memory location. • Character types only store ONE character • Appendix B lists the ASCII characters • Everything needs a name or identifier! • ASCII – American Standard Code for Information Interchange – Variables – Functions – Files • Non-conventional characters: – Newline, \n – Tab, \t ECE102 2-17 ECE102 2-18 User-Defined Identifiers User-Defined Identifiers • User-defined identifiers are identifiers that the programmer makes up • User-Defined Identifier Suggestions for Readability – User-defined identifiers should be meaningful Example: use miles rather than x use area rather than a • User-defined identifiers are used for constants, variable names, and most function names – Use the underscore _ to put space between words • Rules for User-Defined Identifiers – Use uppercase letters to denote constants, lower case to denote variables – – – – – Consist of letters, numbers, and underscores Must begin with a letter or underscore Cannot begin with a digit Cannot be a keyword Only first 31 characters used to distinguish it from other identifiers – An identifier defined in a C standard library should not be redefined – Case sensitive ECE102 • Examples: – – – – – 2-19 ECE102 1Letter Letter_1 Variable Double house footage 2-20 Variable Declaration Variable Declaration • All variables must be declared before they can be used • Each data type has a specific size in memory and a specific way of representing the number or letter • Variables must also have a unique name • Declarations define memory locations, including type of data to be stored, identifer (i.e., name), and possibly an initial value. • General Form to declare variables: data_type identifier_list; • Examples: char ch=‘q’; int age = 20; double x1=1, y1=5, x2=4, y2=7; (initialized as well) double side_1, side_2, distance; (not initialized, do not have values yet) ECE102 2-21 ECE102 2-22 Constant Assignment Statements • Constants are specific values that do not change • Examples of constants 6,371 (radius of earth) 3.1416 • Syntax variable = expression; (π) • Used to assign a value to a variable • Assignment is directional • Symbolic constants are used to name values which do not change during the execution of the program. variable  expression • The computer evaluates the expression on the right and places its value in the memory location represented by the variable on the left • Are always initialized at declaration. • syntax: (no semicolon here) #define identifier value • Example 1: • Examples: #define PI 3.1415926 #define C 2.99792e8 ECE102 side_1 = x2 - x1; – The value 3.0 (=4-1) is placed in the memory location used by the variable side_1. In other words, side_1 equals 3.0 now. • Remember, what is on the right of the ‘=‘ is placed in the variable on the left 2-23 ECE102 2-24 Assignment Operator: = Output to the Screen • Example 2: • We use the printf function to write to the screen sum = 10; item = 5; sum = sum + item; /* item =? – Syntax printf( “format string”, print list); sum =? */ – Example printf(“The distance between the two points is %5.2f \n”, distance); • The following equation doesn’t make sense to C. Why? y2-y1 = side_2; • Example 3: multiple assignments int x, y, z; x=y=0; z=2; • The \n (backslash n) is a line feed. Instructs the computer to print any text that follows on the next line. y=z; x y z x 0 0 y z 0 • The %f is a placeholder for the value of distance, which we would like to see on the screen. ? ? 2 ECE102 2-25 ECE102 Conversion Specifiers for Output Statements 2-26 Display Format • We can specify the field width. • Example: printf(“Results: %3d meters = %4d feet.\n”, meters, feet); Output: Results: _21 meters = __68 feet. • If the number contains more digits than the field width, the field width is ignored. • For a double or float number, the field width includes the decimal point. The precision is the number of digits after the decimal point • The form is %field_width.precisionf • Example: printf(“kilometers = %6.3f\n”, kms); Output (Assume kms = 4.3): kilometers = _4.300 ECE102 2-27 ECE102 2-28 Exercise: printf Example: Conversion • What will the following commands print? #include /*printf, scanf definitions */ #include #define KMS_PER_MILE 1.609 /*conversion constant*/ int main(void) { double miles, /*distance in miles */ kms; /*equivalent distance in km*/ age = 25; gpa = 4.0; printf(“Here is the first line\n”); printf(“I am %d years old, and my GPA is %f\n”, age, gpa); /*Get the distance in miles*/ printf("Enter the distance in miles> "); scanf("%lf",&miles); /*Convert the distance to kilometers*/ kms = KMS_PER_MILE * miles; • %f, by default, means to print a number as a floating point number with 6 digits after the decimal point /*Display the distance in kilometers*/ printf("That equals %f kilometers.\n", kms); system("pause"); return 0; • How do you print out the two points on the screen? – x1=1, y1=5, x2=4, y2=7; ECE102 } 2-29 ECE102 Use scanf_s instead of scanf 2-30 Input from the Keyboard • Can obtain input from the keyboard using the scanf function • Microsoft Visual Studio gives the following error when compiling scanf – error C4996: 'scanf': This function or variable may be unsafe. Consider using scanf_s instead. – Syntax: scanf(format string, input list); – Example: scanf(“%lf”, &miles); • Therefore, use scanf_s in your programs instead of scanf. • When scanf executes, the program pauses until the required data are entered and the key is pressed. • The syntax for these two commands is the same. • Note: the format string is what the function expects to see from the keyboard. We must use: Format Type of variable %c char %d, %i int %f, %e float %lf, %le double ECE102 2-31 ECE102 2-32 Input from the Keyboard Displaying Prompting Message • Use the ampersand (&) in front of the variable names. • scanf does not tell the user what is expected. • The & is the “address of” operator. It returns the address in memory of that variable • scanf can get inputs for multiple variables scanf(“%c%d”, &first_initial, &age); • When scanf executes, the program pauses until the required data are entered and the key is pressed. – scanf expects to be given addresses for variables – It will treat whatever value it is given as an address – This could result in computer crashes and other problems as data is written to a random location 2-33 More Formatting • Right justified (%+): • Left justified (%-): %-d ECE102 2-34 Problem Solving Applied: Velocity Computation %+.2f • Problem statement: during a test flight of an unducted fan (UDF)-powered aircraft, the test pilot has set the engine power level at 40,000 N (newtons), which causes the 20,000-kg aircraft to attain a cruise speed of 180 m/s. The engine throttles are then set to a power level of 60,000 N and the aircraft begins to accelerate. As the speed of the plane increases, the aerodynamic drag increases in proportion to the square of the airspeed. Eventually, the aircraft reaches a new cruise speed where the thrust from the UDF engine is just offset by the drag. The equations used to estimate the velocity and acceleration of the aircraft from the time that the throttle is reset until the plane reaches its new cruise speed are the following: • Escape character \ – – – – printf("Enter the distance in miles> "); scanf("%lf",&miles); • It is important to have a prompt to go with the scanf command. • If you forget the &, what will happen? ECE102 • Displaying prompt: when input data are needed in an interactive program, use the printf function to display a prompting message that tells the user what data to enter. To print backlash: \\ printf(“3\\5”); Question mark: \? printf(“What is your name\?”); Single quote: \’ Double quote: \” printf(“He said, \”Howdy!\”); • Sound bell \a printf(“The bell rings like this. \a”); Velocity  0.0001  time 3  0.0048  time 2  0.75795  time  181.3566; Acceleration  3  0.000062  velocity 2 ECE102 2-35 ECE102 2-36 Problem Solving Applied: Velocity Computation Problem Solving Applied: Velocity Computation • Write a program that asks the user to enter a time value that represents the time elapsed (in seconds) since the power level was increased. Compute and print the corresponding acceleration and velocity of the aircraft at the new time value. Step 2: Analysis: – Input: – Output: Time in seconds – Relevant formulas Acceleration and velocity Step 1: Problem definition Velocity  0.0001  time 3  0.0048  time 2  0.75795  time  181.3566; on  3  0.000062  velocity 2 – Accelerati Problem constants: – Constraints: Visualize the solution: what a user sees who the program is run. None Time >= 0 ECE102 2-37 ECE102 Problem Solving Applied: Velocity Computation 2-38 Algorithms Step 3: Hand examples • An algorithm is the sequence of steps needed to solve a problem Time = 50 seconds Velocity = 208.3 m/s Acceleration = 0.31 m/s2 • Top-down design approach to programming: break a solution into steps, then further refine each one Time = • Generic algorithm for many programs: Velocity = Acceleration = – – – – Get inputs Check validity of inputs Calculate result(s) Display the result(s) • A modular program would consist of functions that implement each step ECE102 2-39 ECE102 2-40 Problem Solving Applied: Velocity Computation Problem Solving Applied: Velocity Computation Step 4a: Pseudo-code (algorithm): step-by-step outline (use variables names in the pseudo-code) 1. Get input data time 2. Computations – Calculate velocity, » Velocity = … – Calculate acceleration, » Acceleration = … 3. Display velocity and acceleration (specify the details here) - display Velocity = …… - display Acceleration = …… • Step 4b: Implementation #include #include int main(void) { double time, velocity, acceleration; /*declare input and outputs*/ /* Get time value from the keyboard. */ printf("Enter new time value in seconds: \n"); scanf("%lf",&time); /* Compute velocity and acceleration. */ velocity = 0.00001*pow(time,3) - 0.00488*pow(time,2) + 0.75795*time + 181.3566; acceleration = 3 - 0.000062*velocity*velocity; /* Print velocity and acceleration. */ printf("Velocity = %8.3f m/s \n",velocity); printf("Acceleration = %8.3f m/s^2 \n",acceleration); Requirement in this class: – – Pseudo-code needs to contain specific information so that someone else can write a program based on it alone. Use variable names picked up in Step 2 (Analysis). ECE102 } 2-41 system (“pause”); return 0; ECE102 Problem Solving Applied: Velocity Computation Arithmetic Operators Step 5: Testing • • • • Enter new time value in seconds: 50 Velocity = 208.304 m/s Acceleration = 0.310m/s^2 Press any key to continue Addition Subtraction Multiplication Division • Modulus + * / % – Modulus returns the remainder of division between two integers – Example 5%2 returns a value of 1 9%3 returns a value of 0 8%5 = 17%3 = Enter new time value in seconds: 100 Velocity = 218.352 m/s Acceleration = 0.044 m/s^2 Press any key to continue . . . ECE102 2-42 2-43 ECE102 2-44 Integer Division Priority of Operators • Division between two integers results in an integer. • The result is truncated, not rounded • Example: • • • • 5/3 is equal to 1 3/6 is equal to 0 • How to get 5/3=1.666…? 5.0/3 or 5/3.0 Convert one number to a floating point using .0! 7+3*5–2= (7 + 3) * 5 – 2 = 4+7/3 8%3*6 • Priority of operators 1. Parentheses 2. Unary operators (+ -) Inner most first Right to left 3. Binary operators (* / %) Left to right 4. Binary operators (+ -) Left to right • Cast operator: (double) 5 / 3 Convert 5 to double before proceeding with the calculation. ECE102 2-45 ECE102 2-46 Math Expressions in C Overflow and Underflow • Add parentheses to ensure the order in which the operators are performed. • Every data type has a limit on the range of allowed values: int maximum = 2,147,483,647 • Overflow – answer too large to store – Example: using 16 bits for integers – result = 32000 +532; 1 1 1 1   R1 R2 R3 • Use parentheses and spaces to enhance the readability of the program. R • Exponent overflow – answer’s exponent too large – Example: using float, with exponent range –38 to 38 – result = 3.25e28 * 1.0e15; • Exponent underflow P2  P1  ECE102 – answer’s exponent to small – Example: using float, with exponent range –38 to 38 – Result = 3.25e-28 *1.0e-15;  v22 ( A22  A12 ) A12 2-47 ECE102 2-48 Data Range : System Limitations /* This program prints the system limitations. #include #include #include int main(void) { /* Print integer type maximums. */ printf("short maximum: %i \n",SHRT_MAX); printf("int maximum: %i \n",INT_MAX); printf("long maximum: %li \n\n",LONG_MAX); Increment and Decrement Operators */ • Increment Operator ++ • post incrementx++; • pre increment ++x; • Decrement Operator - • post decrement • pre decrement --x; /* Print float precision, range, maximum. */ printf("float precision digits: %i \n",FLT_DIG); printf("float maximum exponent: %i \n", FLT_MAX_10_EXP); printf("float maximum: %e \n\n",FLT_MAX); } x--; • For example, • • • • k k x x = 5; m= ++k; both m and k become 6 =5; n = k--; n becomes 5 and k becomes 4 = 3, y = 4; W = ++x – y; w=? = 3, y = 4; W = x++ – y; w=? getchar(); return 0; ECE102 2-49 ECE102 Abbreviated Assignment Operator • operator += -= *= /= %= • Example: b += c + d; x = 2; y = 4; x = 2; y = 4; ECE102 example x x x x x Precedence of Arithmetic and Assignment Operators equivalent statement += 2; -= 2; *= y; /= y; %= y; 2-50 x = x+2; x = x-2; x = x*y; x = x/y; x = x%y; b = ? y %= x; x += y; y = ? y = ? 2-51 ECE102 2-52 Functions in fabs(x) computes absolute value of x sqrt(x) computes square root of x, where x >=0 pow(x,y) computes xy ceil(x) nearest integer larger than x floor(x) nearest integer smaller than x exp(x) computes ex log(x) computes ln x, where x >0 log10(x) computes log10x, where x>0 sin(x) sine of x, where x is in radians cos(x) cosine of x, where x is in radians tan(x) tangent of x, where x is in radians ECE102 2-53

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