diff --git b/common/auxiliar.c a/common/auxiliar.c
new file mode 100644
index 0000000..9adbb20
--- /dev/null
+++ a/common/auxiliar.c
@@ -0,0 +1,123 @@
+#include "auxiliar.h"
+
+char* substring(char *string, uint8_t start, uint8_t end)
+{
+        uint8_t size = end - start;
+        char *substr;
+        substr = (char*) malloc(sizeof(char)*size + 1);
+        memset(substr,0x00,size+1);
+        strncpy(substr,string+start,size);
+        return substr;
+}
+
+int next_occurrence(char *string, char character)
+{
+        int i;
+        int pos = -1;
+        for(i = 0; i < strlen(string); i++)
+        {
+                if(string[i] == character)
+                {
+                        pos = i;
+                        break;
+                }
+        }
+        return pos;
+}
+
+int num_occurrences(char *string, char character)
+{
+        int i;
+        int count = 0;
+        for(i = 0; i < strlen(string); i++)
+        {
+                if(string[i] == character)
+                {
+                        count++;
+                }
+        }
+        if(!count)
+        {
+                return -1;
+        }
+        return count;
+}
+
+void error()
+{
+        printf("error");
+        exit(-1);
+}
+
+char** comma_separate(char *input)
+{
+        int i;
+        int next_pos = 0;
+        int pos = 0;
+        int input_num = num_occurrences(input,',');
+        if(input_num <= 0)
+        {
+                return NULL;
+        }
+        char **inputs;
+        inputs = malloc(sizeof(char*) * input_num);
+        for(i = 0; i < input_num; i++)
+        {
+                next_pos += next_occurrence(input+pos,',');
+                if(next_pos == -1)
+                {
+                        return NULL;
+                }
+                inputs[i] = substring(input,pos,next_pos);
+                next_pos++;
+                pos = next_pos;
+        }
+        return inputs;
+}
+
+void free_mem(char **inputs, int num_inputs)
+{
+        int i;
+        for(i = 0; i < num_inputs; i++)
+        {
+                free(inputs[i]);
+        }
+        free(inputs);
+}	
+
+int last_occurrence(char *string, char character)
+{
+	int i;
+	int pos = -1;
+	for(i = 0; i < strlen(string); i++)
+	{
+		if(string[i] == character)
+		{
+			pos = i;
+		}
+	}
+	return pos;
+}
+
+void normalize(char **inputs, int num_inputs)
+{
+        int i;
+        int j;
+        int length;
+
+        for(i = 0; i < num_inputs; i++)
+        {
+                length = strlen(inputs[i]);             
+                for(j = 0; j < length; j++)
+                {
+                        if(inputs[i][j] == '0')
+                        {
+                                inputs[i][j] = 0;
+                        }
+                        else
+                        {
+                                inputs[i][j] = 1;
+                        }
+                }
+        }
+}
\ No newline at end of file
diff --git b/common/auxiliar.h a/common/auxiliar.h
new file mode 100644
index 0000000..b3eb016
--- /dev/null
+++ a/common/auxiliar.h
@@ -0,0 +1,15 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+char* substring(char *string, uint8_t start, uint8_t end);
+int next_occurrence(char *string, char character);
+int num_occurrences(char *string, char character);
+int last_occurrence(char *string, char character);
+char** comma_separate(char *input);
+
+void error();
+void free_mem(char **inputs, int num_inputs);
+
+void normalize(char **inputs, int num_inputs);
diff --git b/examples/multiplexor2.sh a/examples/multiplexor2.sh
new file mode 100755
index 0000000..977fddc
--- /dev/null
+++ a/examples/multiplexor2.sh
@@ -0,0 +1,13 @@
+#!/bin/bash
+
+INPUT="$1"
+A=`echo "$INPUT" | cut -d',' -f 1`
+B=`echo "$INPUT" | cut -d',' -f 2`
+S=`echo "$INPUT" | cut -d',' -f 3`
+
+N1=`./not $S,`
+N2=`./and $N1,$A,`
+N3=`./and $S,$B,`
+Z=`./or $N2,$N3,`
+
+echo $Z
diff --git b/examples/multiplexor4.sh a/examples/multiplexor4.sh
new file mode 100755
index 0000000..bfe2407
--- /dev/null
+++ a/examples/multiplexor4.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+
+INPUT="$1"
+
+A=`echo "$INPUT" | cut -d',' -f 1`
+B=`echo "$INPUT" | cut -d',' -f 2`
+C=`echo "$INPUT" | cut -d',' -f 3`
+D=`echo "$INPUT" | cut -d',' -f 4`
+S=`echo "$INPUT" | cut -d',' -f 5`
+
+S1=`echo "$S" | cut -b1`
+S2=`echo "$S" | cut -b2`
+
+N1=`./not $S1,`
+N2=`./not $S2,`
+N3=`./and $D,$S1,`
+N4=`./and $C,$N1,`
+N5=`./and $B,$S1,`
+N6=`./and $A,$N1,`
+N7=`./and $N3,$S2,`
+N8=`./and $N4,$S2,`
+N9=`./and $N5,$N2,`
+N10=`./and $N6,$N2,`
+N11=`./or $N7,$N8,`
+N12=`./or $N9,$N10,`
+Z=`./or $N11,$N12,`
+
+echo $Z
diff --git b/logic_gate/Makefile a/logic_gate/Makefile
new file mode 100644
index 0000000..22b7203
--- /dev/null
+++ a/logic_gate/Makefile
@@ -0,0 +1,21 @@
+SYMLINKS = or nor xor xnor not and nand
+TARGETS = logic_gate
+
+.PHONY: all clean
+
+all: $(TARGETS) symlinks
+
+clean:
+	rm -rf $(TARGETS) $(SYMLINKS)
+
+symlinks: logic_gate
+	ln -s logic_gate or
+	ln -s logic_gate nor
+	ln -s logic_gate xor
+	ln -s logic_gate xnor
+	ln -s logic_gate not
+	ln -s logic_gate and
+	ln -s logic_gate nand
+
+logic_gate:
+	gcc -I../common/ ../common/auxiliar.c logic_gate.c -o logic_gate
diff --git b/logic_gate/logic_gate.c a/logic_gate/logic_gate.c
new file mode 100644
index 0000000..e9ef26b
--- /dev/null
+++ a/logic_gate/logic_gate.c
@@ -0,0 +1,259 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include "auxiliar.h"
+
+int check_length(char **inputs, uint8_t num_inputs)
+{
+        int i;
+        int length = strlen(inputs[0]);
+        for(i = 1; i < num_inputs; i++)
+        {
+                if(strlen(inputs[i]) != length)
+                {
+                        return -1;
+                }
+        }
+        return length;
+}
+
+char* or(char **inputs, int num_inputs, int input_length)
+{
+	int i;
+	int j;
+	char *result = malloc(sizeof(char) * input_length + 1);
+	memset(result, 0x00, input_length);
+	for(i = 0; i < input_length; i++)
+	{
+		for(j = 0; j < num_inputs; j++)
+		{
+			result[i] |= inputs[j][i];
+		}
+		if(result[i])
+		{
+			result[i] = '1';
+		}
+		else
+		{
+			result[i] = '0';
+		}
+
+	}
+	return result;
+}
+
+char* nor(char **inputs, int num_inputs, int input_length)
+{
+	int i;
+	int j;
+	char *result = malloc(sizeof(char) * input_length + 1);
+	memset(result, 0x00, input_length);
+	for(i = 0; i < input_length; i++)
+	{
+		for(j = 0; j < num_inputs; j++)
+		{
+			result[i] |= inputs[j][i];
+		
+		}
+		if(result[i])
+		{
+			result[i] = '0';
+		}
+		else
+		{
+			result[i] = '1';
+		}
+	}
+    return result;
+}
+
+char* xor(char **inputs, int num_inputs, int input_length)
+{
+	int i;
+	int j;
+	char *result = malloc(sizeof(char) * input_length + 1);
+	memset(result, 0x00, input_length);
+	for(i = 0; i < input_length; i++)
+	{
+		for(j = 0; j < num_inputs; j++)
+		{
+			result[i] ^= inputs[j][i];
+		}
+		if(result[i])
+		{
+			result[i] = '1';
+		}
+		else
+		{
+			result[i] = '0';
+		}
+	}
+    return result;
+}
+
+char* xnor(char **inputs, int num_inputs, int input_length)
+{
+	int i;
+	int j;
+	char *result = malloc(sizeof(char) * input_length + 1);
+	memset(result, 0x00, input_length);
+	for(i = 0; i < input_length; i++)
+	{
+		for(j = 0; j < num_inputs; j++)
+		{
+			result[i] ^= inputs[j][i];
+		}
+		if(result[i])
+		{
+			result[i] = '0';
+		}
+		else
+		{
+			result[i] = '1';
+		}
+	}
+    return result;
+}
+
+char* and(char **inputs, int num_inputs, int input_length)
+{
+	int i;
+	int j;
+	char *result = malloc(sizeof(char) * input_length + 1);
+	memset(result, 0x01, input_length);
+	for(i = 0; i < input_length; i++)
+	{
+		for(j = 0; j < num_inputs; j++)
+		{
+			result[i] &= inputs[j][i];
+		}
+		if(result[i])
+		{
+			result[i] = '1';
+		}
+		else
+		{
+			result[i] = '0';
+		}
+	}
+    return result;
+}
+
+char* nand(char **inputs, int num_inputs, int input_length)
+{
+	int i;
+	int j;
+	char *result = malloc(sizeof(char) * input_length + 1);
+	memset(result, 0x01, input_length);
+	for(i = 0; i < input_length; i++)
+	{
+		for(j = 0; j < num_inputs; j++)
+		{
+			result[i] &= inputs[j][i];
+		}
+		if(result[i])
+		{
+			result[i] = '0';
+		}
+		else
+		{
+			result[i] = '1';
+		}
+	}
+    return result;
+}
+
+char* not(char **inputs, int num_inputs, int input_length)
+{
+	int i;
+	int j;
+	char *result = malloc(sizeof(char) * input_length + 1);
+	memset(result, 0x01, input_length);
+	for(i = 0; i < input_length; i++)
+	{
+		for(j = 0; j < num_inputs; j++)
+		{
+			result[i] = inputs[j][i];			
+		}
+		if(result[i])
+		{
+			result[i] = '0';
+		}
+		else
+		{
+			result[i] = '1';
+		}
+	}
+    return result;
+}
+
+int main(int argc, char **argv)
+{
+	if(argc != 2)
+	{
+		error();
+	}
+	char *input = argv[1];
+	if(!strcmp(input,"error"))
+	{
+		error();
+	}
+	char **inputs = comma_separate(input);
+	if(inputs == NULL)
+	{
+		error();
+	}
+	int num_inputs = num_occurrences(input,',');
+	int input_length = check_length(inputs,num_inputs);
+	if(input_length == -1)
+	{
+		error();
+	}
+	normalize(inputs,num_inputs);
+	char *result;
+	char *command_name;
+	if(last_occurrence(argv[0],'/') == -1)
+	{
+		command_name = argv[0];
+	}
+	else
+	{
+		command_name = substring(argv[0],last_occurrence(argv[0],'/')+1,strlen(argv[0]));
+	}
+	if(!strcmp(command_name,"or"))
+	{
+		result = or(inputs,num_inputs,input_length);
+	}
+	else if(!strcmp(command_name,"nor"))
+	{
+		result = nor(inputs,num_inputs,input_length);
+	}
+	else if(!strcmp(command_name,"xor"))
+	{
+		result = xor(inputs,num_inputs,input_length);
+	}
+	else if(!strcmp(command_name,"xnor"))
+	{
+		result = xnor(inputs,num_inputs,input_length);
+	}
+	else if(!strcmp(command_name,"and"))
+	{
+		result = and(inputs,num_inputs,input_length);
+	}
+	else if(!strcmp(command_name,"nand"))
+	{
+		result = nand(inputs,num_inputs,input_length);
+	}
+	else if(!strcmp(command_name,"not"))
+	{
+		result = not(inputs,num_inputs,input_length);
+	}
+	else
+	{
+		error();
+	}
+	free_mem(inputs,num_inputs);
+	printf("%s",result);
+	free(result);
+	return 0;
+}
diff --git b/plexers/Makefile a/plexers/Makefile
new file mode 100644
index 0000000..3229256
--- /dev/null
+++ a/plexers/Makefile
@@ -0,0 +1,11 @@
+TARGETS = multiplexor
+
+.PHONY: all clean
+
+all: $(TARGETS)
+
+clean:
+	rm -rf $(TARGETS)
+
+multiplexor:
+	gcc -I../common/ ../common/auxiliar.c multiplexor.c -o multiplexor -lm
diff --git b/plexers/multiplexor a/plexers/multiplexor
new file mode 100755
index 0000000..181bc09
--- /dev/null
+++ a/plexers/multiplexor
diff --git b/plexers/multiplexor.c a/plexers/multiplexor.c
new file mode 100644
index 0000000..0d8dde0
--- /dev/null
+++ a/plexers/multiplexor.c
@@ -0,0 +1,83 @@
+#include <stdio.h>
+#include <string.h>
+#include "auxiliar.h"
+#include <math.h>
+
+int bin2dec(char *bin)
+{
+	int i;
+	int num = 0;
+	int length = strlen(bin);
+	int pos = length - 1;
+	char *aux = (char*) malloc(sizeof(char) * length);
+	strcpy(aux,bin);
+	normalize(&aux,1);
+	for(i = 0; i < length; i++)
+	{
+		if(aux[pos--])
+		{
+			num += pow(2,i);
+		}
+	}
+	free(aux);
+	return num;
+}
+
+int check_length(char **inputs, uint8_t num_inputs)
+{
+        int i;
+        int length = strlen(inputs[0]);
+        for(i = 1; i < num_inputs-1; i++)
+        {
+                if(strlen(inputs[i]) != length)
+                {
+                        return -1;
+                }
+        }
+        int sel_length = strlen(inputs[num_inputs-1]);
+        if(pow(2,sel_length) < (num_inputs-1))
+        {
+        	return -1;
+        }
+        return length;
+}
+
+int main(int argc, char **argv)
+{
+	int i;
+	if(argc != 2)
+	{
+		error();
+	}
+	char *input = argv[1];
+	if(!strcmp(input,"error"))
+	{
+		error();
+	}
+	char **inputs = comma_separate(input);
+	if(inputs == NULL)
+	{
+		error();
+	}
+	int num_inputs = num_occurrences(input,',');
+	int input_length = check_length(inputs,num_inputs);
+	if(input_length == -1)
+	{
+		error();
+	}
+	int selected = bin2dec(inputs[num_inputs-1]);
+	if(selected >= (num_inputs-1))
+	{
+		for(i = 0; i < input_length; i++)
+		{
+			printf("0");
+		}
+	}
+	else
+	{
+		char *result = inputs[selected];
+		printf("%s",result);
+	}
+	free_mem(inputs,num_inputs);
+	return 0;
+}
diff --git b/todo a/todo
new file mode 100644
index 0000000..970a6f4
--- /dev/null
+++ a/todo
@@ -0,0 +1,29 @@
+demuxer
+coder
+decoder
+bit selector
+
+adder
+substractor
+multiplier
+divider
+negator
+comparator
+shifter
+bit adder
+bit finder
+
+biestable t
+biestable d
+biestable jk
+biestable sr
+register
+counter
+shift register
+ram
+rom
+
+
+7seg
+tty
+led