modifications to pi project

README.md

@@ -61,8 +61,11 @@ the 64 bit ARM Instruction Set Architecture (ISA).
 | .... a | [.... Alignment](./section_1/structs/alignment.md) |
 | .... b | [.... Defining](./section_1/structs/defining.md) |
 | .... c | [.... Using](./section_1/structs/using.md) |
-| 8 | [`const`](./section_1/const/README.md)
+|  8 | [`const`](./section_1/const/README.md)
-| 9 | [Casting](./section_1/casting/README.md) |
+|  9 | [Casting](./section_1/casting/README.md) |
+| 10 | Floating Point |
+| .... a | [ .... What Are Floating Point Numbers? ](./section1/float/what.md)
+
 
 ## Section 2 - Stuff
 

projects/PI/README.md

@@ -24,11 +24,11 @@ must multiply by 4 at the end.
 This will come from the command line as in:
 
 ```text
-user@comporg:~/pi $ ./a.out 100000
+~/pi $ ./a.out 100000
 Executing: 100000 iterations.
 Hits: 78443
 Approximation: 3.137720
-user@comporg:~/pi $
+~/pi $
 ```
 
 If the command line argument is *not* given, use a default of 100000.
@@ -39,7 +39,8 @@ Remember that all AARCH64 instructions are 32 bits long. An implication of this
 	mov			x0, 1000000
 ```
 
-Since the constant cannot fit along with op codes into four bytes. A way to get around this that comes readily to mind
+Since the constant cannot fit along with op codes into four bytes.
+A way to get around this that comes readily to mind
 is to put the constant in RAM and `ldr` it into a register.
 
 ## Vetting the command line argument
@@ -69,12 +70,12 @@ You must seed the RNG in this way. But in assembly language.
 C and C++ you would do:
 
 ```c++
-// Produces result between 0 and very very close to 1.
+// Produces result between 0 and 1.
 float v = float(rand()) / float(RAND_MAX);
 ```
 
 You must do this in your program. What value is RAND_MAX? Write a tiny C++ program on the ARM and print out the value. Or, put
-`RANDMAX` into an IDE and ask the IDE to locate the definition.
+`RANDMAX` into an IDE and ask the IDE to locate its definition.
 
 You must write a subroutine (function) which returns a random number in the right range. Call it `randf` so I can find it easily.
 
@@ -97,6 +98,63 @@ restored in functions.
 
 You'll use instructions like `fmul`, `fdiv`, `fsqrt`, `fmov` and `fcmp`.
 
+## Aliases For Registers
+
+We have previously advised you to create a "bible" documenting
+which registers are used for what. Here is another way of aiding
+you to:
+
+* better understand your code, and
+
+* avoid using the wrong register in an instruction.
+
+The idea is to give specific registers aliases, symbolic names
+that mean something to your code rather than just a letter and
+number. Here is an example:
+
+```asm
+LOOP_MX .req        x19
+LOOP_CT .req        x20
+HITS    .req        x21
+
+RND_MF  .req        d20
+DTMP    .req        d21
+```
+
 ## Printing FP
 
 `printf` will be your friend. Like always, the format string address goes in `x0`. A `%f` found in the format string tells `printf` to look in the FP registers starting with `d0` as the first value.
+
+## Added Challenge
+
+The program as specified above will print its result only at
+the end of its computation. If you specify a very large number
+of loops, this can take a long time. The shell prompt will
+just sit and you won't know if your program is working or
+not.
+
+As an added challenge, add functionality that tests the
+loop counter and from time to time, such as every 2048
+loops, prints the results so far.
+
+Note that this can produce a lot of lines of output. To
+deal with this, create a single line format string (for
+`printf()`) that also prints some *old school* cursor
+control sequences.
+
+Add this to your single line intermediate results:
+
+```text
+\033[1;1H\033[2J
+```
+
+These characters will be interpreted by the terminal
+(console) as meaning:
+
+* Move the cursor to line 1 column 1, and
+
+* Erase everything below this position.
+
+`\033` is the ESCAPE character represented by its
+value in *octal*. *Octal* is indicated by the leading
+bash (back slash) and the leading 0.