Basically there are two ways of using Input Output devices , first is by using non interrupt programming and other one is by using interrupts, in this we will use non interrupt way-&gt;
Let us take following example
<h1 id="heading-write-risc-style-program-for-performing-typing-by-keyboard-and-displaying-it-on-screen">Write RISC style program for performing typing by keyboard and displaying it on screen</h1>
1.Initialize the pointer register R2 so that characters pressed by keyboards are placed in that address in main memory
<pre><code>Move R2,#LOC
</code></pre>2.Load the end character in register which suggests that typing is over
<pre><code>MoveByte R3,#CR
</code></pre>3.Wait for character to be entered
<pre><code>LoadByte R4,KBD_STATUS
</code></pre>4.Check the status of flag
<pre><code>And R4,R4,#2
</code></pre>5.If flag is not set or keyboard is not ready then again read the status flag
<pre><code>Branch_if_[R4] = 0 READ
</code></pre>6.Load all data from keyboard register to microprocessor register
<pre><code>LoadByte R5,KBD_DATA
</code></pre>7.Store the character read from keyboard in main memory
<pre><code>StoreByte R5,[R2]
</code></pre>8.Increment the address pointer in main memory
<pre><code>Add R2,R2,#1
</code></pre>9. Wait for display to be ready
<pre><code>LoadByte R4,DISP_STATUS
</code></pre>10.Check the output status flag
<pre><code>And R4,R4,#4
</code></pre>11.If it is not ready then repeat the checking process
<pre><code>Branch_if_[R4] = 0 ECHO
</code></pre>12.Store the value in register in address at keyboard device
<pre><code>StoreByte R5,DISP_DATA
</code></pre>13.Check for ending condition , if not ended then repeat read &amp; write process
<pre><code>Branch_if_[R5]!=[R3] READ
</code></pre>

Basically there are two ways of using Input Output devices , first is by using non interrupt programming and other one is by using interrupts, in this we will use non interrupt way->

Let us take following example

# Write RISC style program for performing typing by keyboard and displaying it on screen

**1.Initialize the pointer register R2 so that characters pressed by keyboards are placed in that address in main memory**

```
Move R2,#LOC
```

**2.Load the end character in register which suggests that typing is over**

```
MoveByte R3,#CR
```

**3.Wait for character to be entered**

```
LoadByte R4,KBD_STATUS
```

**4.Check the status of flag**

```
And R4,R4,#2
```

**5.If flag is not set or keyboard is not ready then again read the status flag**

```
Branch_if_[R4] = 0 READ
```

**6.Load all data from keyboard register to microprocessor register**

```
LoadByte R5,KBD_DATA
```
7.Store the character read from keyboard in main memory

```
StoreByte  R5,[R2]
```
**8.Increment the address pointer in main memory**
```
Add R2,R2,#1
```
**9. Wait for display to be ready**

```
LoadByte R4,DISP_STATUS
```
**10.Check the output status flag**

```
And R4,R4,#4
```

**11.If it is not ready then repeat the checking process**

```
Branch_if_[R4] = 0 ECHO
```

**12.Store the value in register in address at keyboard device**

```
StoreByte R5,DISP_DATA
```

**13.Check for ending condition , if not ended then repeat read & write process**

```
Branch_if_[R5]!=[R3] READ
```





How do Input Output devices work with Computer (Non interrupt edition)

Write RISC style program for performing typing by keyboard and displaying it on screen