Diff: main.cpp

Revision:

111:956b1c606b66

Parent:

110:22b71c32c5e1

Child:

112:c7c727d92f2a

--- a/main.cpp	Fri Oct 01 03:03:36 2021 +0000
+++ b/main.cpp	Mon Oct 11 12:15:03 2021 +0000
@@ -1,27 +1,52 @@
 /*
-Project: 21_TimerTest1_v5
+Project: 21_FuncEx_v5
 File: main.cpp
+
+ This simple program demonstrates that C passes arguments by value.
  
-Explores timer behavior. Each loop takes about 24 mS. Most of this time is 
-likely spent doing the serial output.
+ See http://www.csie.ntu.edu.tw/~r92094/c++/VT100.html and/or 
+ https://gist.github.com/fnky/458719343aabd01cfb17a3a4f7296797 for escape 
+ sequences.
  
-Last modified 9/30/21 by C. S. Tritt (v. 1.0)
+ Written by: Dr. C. S. Tritt; Last revised 10/11/21 (v. 1.2)
 */
 #include "mbed.h"
 
-// Construct a timer object.
-Timer myTimer;
-// Construct a transmit only serial connection over our USB.
-Serial pc(USBTX, NC, 9600);
- 
-int main()
-{
-    myTimer.start();  // Start the timer.
- 
-    for (int i = 1; i <= 20; i++) { // Main loop.
-        // Save the time on timer.
-        float current_time = myTimer.read();   
-        // Send the time as text via the serial port.
-        pc.printf("Time %f seconds.\n",current_time );
+// Function definitions are typically in .h files are more commonly that are 
+// included here.
+int myFunc(int x, int y); // Function declaration required.
+
+Serial pc(USBTX, USBRX, 9600); // Create Serial object.
+
+const char ESC=27; // ESC character for ANSI escape sequences.
+const int DELAY = 2000; // Loop delay in mS.
+
+int main() {
+    while(true) {
+        // Clear screen & move cursor to upper left ANSI/VT100 sequence.
+        pc.printf("%c[2J", ESC); pc.printf("%c[H", ESC);
+        // Start of display code.
+        pc.printf("In function demo main...\n");        
+        int a = 5; // Create and initialize a.
+        pc.printf("a = %d\n", a); // Display a.
+        int b = 6; // Create and initialize b.
+        pc.printf("b = %d\n", b); // Display b.
+        pc.printf("About to call my function.\n");
+        int c = myFunc(a, b); // Call my function.
+        pc.printf("Function has returned.\n");
+        pc.printf("a = %d\n", a); // Redisplay a.
+        pc.printf("b = %d\n", b); // Redisplay b.               
+        pc.printf("c = %d\n", c); // Display b.
+        ThisThread::sleep_for(DELAY); // Pause for DELAY mS.
     }
-}
\ No newline at end of file
+}
+
+int myFunc(int x, int y) { // Function definition. Often in separate files!
+    int z = x + y;
+    // Changing parameter values here won't change argument values in main!
+    x = 50;
+    pc.printf("x = %d\n", x); // Generally don't put I/O in regular functions.
+    y = 100;
+    pc.printf("y = %d\n", y); // Generally don't put I/O in regular functions.
+    return z; // Explicit return is required in C/C++. 
+}    
\ No newline at end of file