Creating A Parking Sensor, Need A Kick Start, Using C

Hey guys, im new to this forum and arduino (just a little hobby) was after a bit of help. I'm using the Arduino Uno board and trying to reprogram it using C.
I've successfully created a counter (increases numbers each time a button is pressed, displaying count on 7 seg led), and just finished creating a stopwatch (Total nightmare lol). So I am a noob at this unfortunately but getting there it seems.
I've just picked up a sensor (ultra sonic I believe) and was looking to see if I can imitate a parking sensor, using C programming language, im using a software called Altera Nios II, just looking for some help on how to read the sensor, I've done a bit of research and I believe the output will be in clock cycles which im sure I can figure out how to convert to cm and display on the 7 seg led.

All help is appreciated!

google +ping))) + arduino

Hey, thanks for the fast reply, I've checked out ping however the coding is for use with the arduino software, I was after some C code?

Below is the code from the tutorial section;

/* Ping))) Sensor
  
   This sketch reads a PING))) ultrasonic rangefinder and returns the
   distance to the closest object in range. To do this, it sends a pulse
   to the sensor to initiate a reading, then listens for a pulse 
   to return.  The length of the returning pulse is proportional to 
   the distance of the object from the sensor.
     
   The circuit:
    * +V connection of the PING))) attached to +5V
    * GND connection of the PING))) attached to ground
    * SIG connection of the PING))) attached to digital pin 7

   http://www.arduino.cc/en/Tutorial/Ping
   
   created 3 Nov 2008
   by David A. Mellis
   modified 30 Aug 2011
   by Tom Igoe
 
   This example code is in the public domain.

 */

// this constant won't change.  It's the pin number
// of the sensor's output:
const int pingPin = 7;

void setup() {
  // initialize serial communication:
  Serial.begin(9600);
}

void loop()
{
  // establish variables for duration of the ping, 
  // and the distance result in inches and centimeters:
  long duration, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance
  inches = microsecondsToInches(duration);
  cm = microsecondsToCentimeters(duration);
  
  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();
  
  delay(100);
}

long microsecondsToInches(long microseconds)
{
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
  return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds)
{
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}

If anyone knows any converter to plain C code that would be perfect!

If there are any C users who can interpret this into C please help XD

90% is plain C
which statement causes problems?

OUTPUT, HIGH, LOW, Serial, pingPin; all return the same error "undeclared"

microsecondsToCentimeters and microsecondsToInches; both return the error "conflicting types"