ES101 - Lesson 3 : scanf - Revision history

Proj user22: /* Common Mistake */

2019-11-11T21:53:43Z

‎Common Mistake

Preet: /* Assignment */

2013-08-08T06:02:15Z

‎Assignment

Preet: /* Assignment */

2013-08-08T06:01:18Z

‎Assignment

Preet: /* Assignment */

2013-06-19T18:12:37Z

‎Assignment

Preet: /* Assignment */

2013-06-10T21:37:20Z

‎Assignment

Preet: /* scanf */

2013-02-15T22:54:25Z

‎scanf

Preet: /* scanf */

2013-02-15T22:53:41Z

‎scanf

Preet at 18:48, 21 September 2012

2012-09-21T18:48:43Z

Preet: /* Assignment */

2012-09-21T18:45:42Z

‎Assignment

Preet: /* scanf */

2012-09-18T00:57:02Z

‎scanf

@@ Line 60: / Line 60: @@
 scanf("%i", &weight_lb);
-printf("Your weight in kg: %i\n", wieght_kg);
+printf("Your weight in kg: %i\n", weight_kg);
 </syntaxhighlight>

@@ Line 73: / Line 73: @@
 *  Also note that after you open the COM Port in Hercules, the reset button should be pressed on the Board to restart the program otherwise you might miss the output if you open the COM port too late.
-'''Note for future labs'''
+'''Note for future labs''' :
 Normally, your future labs will build on previous labs.  In case you want to preserve your old code, just rename the old '''main()''' function to something earlier such as '''lab3''' and write a new '''main''' function.  '''Note that there can only be ONE main() function per program.'''
 We will improve the percentage calculator by allowing a user to input values for us:
 #  Declare the following float variables :

@@ Line 67: / Line 67: @@
 == Assignment ==
-To provide input to your Board from your computer's PC, you need to open '''Hercules''' Program at 38400bps by going to the Serial Tab.  To enter input, you can simply type on the '''Hercules''' window and hit the <Enter key> to enter text from your keyboard, which will be transmitted to the Board. Also note that after you open the COM Port in Hercules, the reset button should be pressed on the Board to restart the program.
+You should setup Hercules to make sure you can provide input to the board correctly :
 We will improve the percentage calculator by allowing a user to input values for us:

@@ Line 79: / Line 79: @@
 # Display "Program finished, press any key to quit ..."
 #: Test to be sure that the program quits only when a user presses a key.
 <br/>

@@ Line 67: / Line 67: @@
 == Assignment ==
-To provide input to your Board from your computer's PC, you need to open '''Hercules''' Program at 38400bps by going to the Serial Tab.  To enter input, you can simply type on the '''Hercules''' window and hit the Enter key to enter text from your keyboard, which will be transmitted to the Board. Also note that after you open the COM Port in Hercules, the reset button should be pressed on the Board to restart the program.
+To provide input to your Board from your computer's PC, you need to open '''Hercules''' Program at 38400bps by going to the Serial Tab.  To enter input, you can simply type on the '''Hercules''' window and hit the <Enter key> to enter text from your keyboard, which will be transmitted to the Board. Also note that after you open the COM Port in Hercules, the reset button should be pressed on the Board to restart the program.
-# Declare four variables and choose their appropriate type, such as int, or float. Use a meaningful name based on the following uses:
+We will improve the percentage calculator by allowing a user to input values for us:
-#* A variable to store the age (in years) of the user
+#  Declare the following float variables :
-#* A variable to store the age in months.
+#*  Maximum exam score, user's exam score, and percentage.
-#* A variable to store the height in inches of the user.
+#  Ask the user to input data into your variables, such as:
-#* A variable to store the height in centimeters.
+#*  "What is the max score of your exam: "
-# Ask the user to input their age in years and store it to your age variable.
+#*  "What was your score: "
-# Ask the user to input their height and store it to your height variable in inches.
+# Calculate the percentage and print it out with output similar to:
-# Calculate the age in months and store it to the appropriate variable.
+#*  "You got 45/50 and your percentage is: 90.0%"
-# Calculate the height in centimeters (2.54 cm per inch) and store it to the appropriate variable.
+# Display "Program finished, press any key to quit ..."
 #: Test to be sure that the program quits only when a user presses a key.
 <br/>
 === Questions ===
-*  After completing the assignment, try removing & symbol for the scanf statement that asks for user's height.
+*  After completing the assignment, try removing & symbol for one of the scanf statements.
 *: What is the program output?  Does it work as expected?

@@ Line 32: / Line 32: @@
 <syntaxhighlight lang="c">
-int age;
+int age = 0;
-char my_char;
+char my_char = 0;
 printf("What is your age? ");

@@ Line 12: / Line 12: @@
 <syntaxhighlight lang="c">
-int age;
+int age = 0;
-float height;
+float height = 0;
 printf("What is your age? ");
@@ Line 26: / Line 26: @@
 * '''scanf''' variables after the double quotes have & symbol.
-The & (ampersand) symbol is needed because it is called the address operator. Instead of passing the variable's value, you pass the variable's address such that scanf can input the data into the memory location given by the variable's address. If you forget to include the & operator, you will experience unexpected results because '''scanf''' would probably input the data at the wrong memory location.
+The & (ampersand) symbol is the '''address''' operator. Instead of passing the variable's value, you pass the variable's address such that scanf can input the data into the memory location of the variable's address. If you forget to include the & operator, you will experience unexpected results because '''scanf''' would probably input the data at the wrong memory location.
-'''scanf''' should be intuitive to understand except when you try to scanf a single character (%c).  What happens is that a previous '''scanf''' does not consume the <Enter key> character (0x0A) and the next '''scanf''' picks up this character when you try to use: <code>scanf("%c", &my_char);</code>.  To solve this problem a call to getchar() is made, which discards this unconsumed hanging character, and '''scanf''' will wait for a new character from '''Hercules''' terminal.
+'''scanf''' should be intuitive to understand except when you try to scanf a single character (%c).  What happens is that a prior '''scanf''' does not consume the <Enter key> character (0x0A) and the next '''scanf''' picks up this character when you try to use: <code>scanf("%c", &my_char);</code>.  To solve this problem a call to getchar() is made, which discards this unconsumed hanging character, and '''scanf''' will wait for a new character from '''Hercules''' terminal.
@@ Line 54: / Line 54: @@
 Your code is executed sequentially so do not try to assign variables before asking for input:
 <syntaxhighlight lang="c">
-int weight_lb;
+int weight_lb = 0;
 int weight_kg = weight_lb * 1.6; // <-- Assigning this too early!
@@ Line 65: / Line 65: @@
 <br/>
 == Assignment ==
 To provide input to your Board from your computer's PC, you need to open '''Hercules''' Program at 38400bps by going to the Serial Tab.  To enter input, you can simply type on the '''Hercules''' window and hit the Enter key to enter text from your keyboard, which will be transmitted to the Board. Also note that after you open the COM Port in Hercules, the reset button should be pressed on the Board to restart the program.

@@ Line 40: / Line 40: @@
 /**
   * This code will completely skip over the prompt.
-  * If you insert getchar(); before the next scanf() statement,
+  * If you insert getchar(); *twice* before the next scanf() statement,
-  * then it will work as expected as the 'dangling' <enter key>
+  * then it will work as expected as the 'dangling' <enter key> characters
   * will be discarded and scanf will be forced to look for new input.
   */
@@ Line 51: / Line 51: @@
 <br/>
 == Assignment ==
 To provide input to your Board from your computer's PC, you need to open '''Hercules''' Program at 38400bps by going to the Serial Tab.  To enter input, you can simply type on the '''Hercules''' window and hit the Enter key to enter text from your keyboard, which will be transmitted to the Board. Also note that after you open the COM Port in Hercules, the reset button should be pressed on the Board to restart the program.

@@ Line 66: / Line 66: @@
 # Output the user's age in months and years, height in inches, and height in centimeters.
 #* The height in centimeters should only display 2 decimal digits.
 <br/>
@@ Line 71: / Line 74: @@
 *  After completing the assignment, try removing & symbol for the scanf statement that asks for user's height.
 *: What is the program output?  Does it work as expected?

@@ Line 39: / Line 39: @@
 /**
-  * This code will not function unless you insert:
+  * This code will completely skip over the prompt.
-  * getchar(); before the next scanf() statement
+  * If you insert getchar(); before the next scanf() statement,
   */
 printf("Press any key: ");