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--- tanszek:oktatas:techcomm:parity_check [2024/10/06 17:49] – [Example] knehez
+++ tanszek:oktatas:techcomm:parity_check [2025/10/27 18:59] (current) – [Parity Check] knehez
@@ Line 1: / Line 1: @@
 ===== Parity Check =====
-A parity check is a simple error detection mechanism used in digital communication and data storage to detect errors in transmitted or stored data. It ensures that the number of bits with a value of 1 in a binary sequence is either even or odd, depending on the type of parity used.
+A parity check is a simple **error detection** mechanism used in digital communication and data storage to **detect errors** in transmitted or stored data. It ensures that the number of bits with a value of 1 in a binary sequence is either even or odd, depending on the type of parity used.
 There are two types of parity:
@@ Line 41: / Line 41: @@
   * **Limited error detection**: Parity checks can only detect single-bit errors (if one bit flips). It cannot detect multi-bit errors, where two or more bits are changed.
   * **No error correction**: Parity checks only detect errors but cannot correct them. For correction, more advanced techniques like Hamming codes.
+Let's see a C code to check 8 bits parity.
+<sxh c>
+#include <stdio.h>
+int check_parity(unsigned char num) {
+    int count = 0;
+    // Count the number of 1 bits
+    while (num) {
+        count += num & 1;
+        num >>= 1;
+    }
+    // If the count of 1 bits is even, the parity is correct
+    return (count % 2 == 0);
+}
+int main() {
+    char binary[9]; // 8 bits + 1 space for the null terminator
+    unsigned char num = 0;
+    printf("Enter an 8-bit binary number: ");
+    scanf("%8s", binary);
+    // Convert the binary string to an 8-bit unsigned integer
+    for (int i = 0; i < 8; i++) {
+        num <<= 1;                // Shift bits to the left by one position
+        if (binary[i] == '1') {
+            num |= 1;             // Set the lowest bit if the current character is '1'
+        }
+    }
+    if (check_parity(num)) {
+        printf("Parity is correct (even number of 1 bits).\n");
+    } else {
+        printf("Parity is incorrect (odd number of 1 bits).\n");
+    }
+    return 0;
+}
+</sxh>