diff --git a/.gitignore b/.gitignore
index 78634e5..efa0f62 100644
--- a/.gitignore
+++ b/.gitignore
@@ -57,3 +57,7 @@ bin
 */bin
 obj
 */obj
+CMakeFiles
+build
+CMakeCache.txt
+Makefile
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..0d64c00
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,45 @@
+cmake_minimum_required(VERSION 3.0)
+
+project(base)
+set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+include_directories(${PROJECT_SOURCE_DIR})
+add_executable( abc                  src/abc.c                 ) 
+add_executable( adder                src/adder.c               ) 
+add_executable( args                 src/args.c                ) 
+add_executable( arrToBin             src/arrToBin.c            ) 
+add_executable( ascii                src/ascii.c               ) 
+add_executable( calculator           src/calculator.c          ) 
+add_executable( callreference        src/callreference.c       ) 
+add_executable( complex              src/complex.c             ) 
+add_executable( dividableBy7         src/dividableBy7.c        ) 
+add_executable( structdump           src/structdump.c          ) 
+add_executable( echo                 src/echo.c                ) 
+add_executable( echochar             src/echochar.c            ) 
+add_executable( euler                src/euler.c               ) 
+add_executable( factorial            src/factorial.c           ) 
+add_executable( fail                 src/fail.c                ) 
+add_executable( fread                src/fread.c               ) 
+add_executable( hello-world          src/hello-world.c         ) 
+add_executable( options              src/options.c             ) 
+add_executable( pointermagic         src/pointermagic.c        ) 
+add_executable( primenumbers         src/primenumbers.c        ) 
+add_executable( quersumme            src/quersumme.c           ) 
+add_executable( readfile             src/readfile.c            ) 
+add_executable( redefinition         src/redefinition.c        ) 
+add_executable( redefinition-if      src/redefinition-if.c     ) 
+add_executable( return-specified     src/return-specified.c    ) 
+add_executable( scanf-test           src/scanf-test.c          ) 
+add_executable( scnaf-hex-test       src/scnaf-hex-test.c      ) 
+add_executable( signed-to-unsigned   src/signed-to-unsigned.c  ) 
+add_executable( sizeofs              src/sizeofs.c             ) 
+add_executable( success              src/success.c             ) 
+add_executable( sum                  src/sum.c                 ) 
+add_executable( tabtest              src/tabtest.c             ) 
+add_executable( umlaut               src/umlaut.c              ) 
+add_executable( unary-double-not     src/unary-double-not.c    ) 
+add_executable( warning              src/warning.c             ) 
+add_executable( pointer-arithmetic   src/pointer-arithmetic.c  ) 
+
+target_link_libraries(abc m)    # link libm to abc
diff --git a/abc.c b/abc.c
deleted file mode 100644
index 21e5506..0000000
--- a/abc.c
+++ /dev/null
@@ -1,27 +0,0 @@
-#include <stdio.h>
-#include <math.h>
-#include <complex.h>
-#include <stdlib.h>
-
-int main(int argc, char **argv){
-
-    if(argc<3){
-	printf("not enough args! Ex: ./abc 12 -3 5\n");
-	exit(EXIT_FAILURE);
-    }
-    double a = atoi(argv[1]);
-    double b = atoi(argv[2]);
-    double c = atoi(argv[3]);
-
-    printf("(%f)x²+(%f)x+(%f)=0\n", a, b, c);
-    double l1 = 0, l2 = 0;
-    double cl1 = 0, cl2 = 0;
-    l1=(-b + sqrt((b*b)-(4*a*c)))/(2*a);
-    l2=(-b - sqrt((b*b)-(4*a*c)))/(2*a);
-    cl1=(-b + csqrt((b*b)-(4*a*c)))/(2*a);
-    cl2=(-b - csqrt((b*b)-(4*a*c)))/(2*a);
-    printf("(-%.0f (+-) sqrt[(%.0f²)-(4*%.0f*%.0f)])/2*%.0f\n", b, b, a, c, a);
-    printf("x1=%f	x2=%f\n", l1, l2);
-    printf("(complex mode)\nx1=%fi\tx2=%fi\n", cl1, cl2);
-    return 0;
-}
diff --git a/adder.c b/adder.c
deleted file mode 100644
index f0d22b1..0000000
--- a/adder.c
+++ /dev/null
@@ -1,9 +0,0 @@
-#include <stdio.h>
-
-int main() {
-	int a, b;
-	printf("Please input two integers to be added.\n");
-	scanf("%d %d", &a, &b);
-	printf("%d + %d = %d\n", a, b, a+b);
-	return 0;
-}
diff --git a/args.c b/args.c
deleted file mode 100644
index 853554c..0000000
--- a/args.c
+++ /dev/null
@@ -1,15 +0,0 @@
-#include <stdio.h>
-
-int main(int argc, char* argv[]){
-
-    if(argc==1){
-	printf("Recieved only one argument, idiot");
-	return 1;
-    }
-
-    for(int i = 0; i < argc+1; i++){
-	printf("%d.	[%s]\n", i+1, argv[i]);
-    }
-
-    return 0;
-}
diff --git a/arrToBin.c b/arrToBin.c
deleted file mode 100644
index 8fa42bd..0000000
--- a/arrToBin.c
+++ /dev/null
@@ -1,28 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-
-int main(){
-    // input as single int, output as array of ints with only 0 and 1s 
-
-    char str_i[20];
-    int i;
-    
-    fgets(str_i, 20, stdin);
-    i = strtol(str_i, NULL, 0);
-    printf("%d", i);
-
-    int bin[16] = { -1 };
-    int b;
-
-    printf("[CONTROL]as hex %x\n", i);
-    for(int j = 16; j>0; j--){
-        b = i%2;
-        i /= 2;
-        bin[i] = b;
-    }
-    for(int j = 0; j < 16; j++){
-            printf("%d", bin[j]);
-    }
-    printf("\n");
-    return 0;
-}
diff --git a/ascii.c b/ascii.c
deleted file mode 100644
index d0605ef..0000000
--- a/ascii.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <stdio.h>
-
-int main(){
-    for(int i=0; i<256; i++){
-	printf("(dec)%d\t(hex)0x%02x\t(char)%c\t\n",i,i,i);
-    }
-    return 0;
-}
diff --git a/calculator.c b/calculator.c
deleted file mode 100644
index 535710b..0000000
--- a/calculator.c
+++ /dev/null
@@ -1,49 +0,0 @@
-#include <stdio.h>
-#include <stdint.h>
-#include <stdlib.h>
-
-double factorial(double i) {
-    if(i <= 1) {
-	return 1;
-    }
-    return i * factorial(i - 1);
-}
-
-double power(double a, double b) {
-    double result = a;
-    for(int i=0;i<b;i++){
-	result*=a;
-    }
-    return result;
-}
-
-int main(int argc, char **argv){
-
-    // inputs
-    uint32_t a, b;
-    char op;
-    while(1) {
-	printf("\nPlease input the first number.\n");
-	fflush(stdin);
-    	scanf("%d", &a);
-    	printf("Please input the second number.\n");
-	fflush(stdin);
-    	scanf("%d", &b);
-    	printf("Please select an operation. ( + - * / ^ ! ), e to exit.\n");
-	fflush(stdin);
-    	scanf(" %c", &op);	//The %c conversion specifier won't automatically skip any leading whitespace
-    	
-    	// calculate stuff.
-    	switch(op) {
-    	    case '+': printf("%d + %d = %d\n", a, b, a+b); break;
-    	    case '-': printf("%d - %d = %d\n", a, b, a-b); break;
-    	    case '*': printf("%d * %d = %d\n", a, b, a*b); break;
-    	    case '/': printf("%d / %d = %f\n", a, b, (double)a/(double)b); break;
-    	    case '^': printf("%d^%d = %f\n", a, b, power((double)a,(double)b)); break;
-    	    case '!': printf("%d! = %f\n", a, factorial((double)a)); break;
-	    case 'e': printf("exiting...\n"); return 0;
-    	    //case '%': printf("%d % %d = %d\n", a, b, a%b); break; // idk weird outputs.
-    	    default: printf("no operation recognized.\n"); return 1;
-    	}
-    }
-}
diff --git a/callreference.c b/callreference.c
deleted file mode 100644
index fd736e9..0000000
--- a/callreference.c
+++ /dev/null
@@ -1,22 +0,0 @@
-#include <stdio.h>
-
-int* ref(int *i, int* j, int* result){
-    *result = *i + *j;
-    return result;
-}
-    
-int val(int a, int b){
-    return a+b;
-}
-
-int main(){
-
-    int x = 1000;
-    int y = 337;
-    int z;
-    printf("given: %d\n", x);
-    printf("reference: %d\n", *ref(&x, &y, &z));
-    printf("value: %d\n", val(x, y));
-
-    return 0;
-}
diff --git a/cmake_install.cmake b/cmake_install.cmake
new file mode 100644
index 0000000..934c11e
--- /dev/null
+++ b/cmake_install.cmake
@@ -0,0 +1,54 @@
+# Install script for directory: /home/plex/Documents/code/c/c-basic
+
+# Set the install prefix
+if(NOT DEFINED CMAKE_INSTALL_PREFIX)
+  set(CMAKE_INSTALL_PREFIX "/usr/local")
+endif()
+string(REGEX REPLACE "/$" "" CMAKE_INSTALL_PREFIX "${CMAKE_INSTALL_PREFIX}")
+
+# Set the install configuration name.
+if(NOT DEFINED CMAKE_INSTALL_CONFIG_NAME)
+  if(BUILD_TYPE)
+    string(REGEX REPLACE "^[^A-Za-z0-9_]+" ""
+           CMAKE_INSTALL_CONFIG_NAME "${BUILD_TYPE}")
+  else()
+    set(CMAKE_INSTALL_CONFIG_NAME "")
+  endif()
+  message(STATUS "Install configuration: \"${CMAKE_INSTALL_CONFIG_NAME}\"")
+endif()
+
+# Set the component getting installed.
+if(NOT CMAKE_INSTALL_COMPONENT)
+  if(COMPONENT)
+    message(STATUS "Install component: \"${COMPONENT}\"")
+    set(CMAKE_INSTALL_COMPONENT "${COMPONENT}")
+  else()
+    set(CMAKE_INSTALL_COMPONENT)
+  endif()
+endif()
+
+# Install shared libraries without execute permission?
+if(NOT DEFINED CMAKE_INSTALL_SO_NO_EXE)
+  set(CMAKE_INSTALL_SO_NO_EXE "0")
+endif()
+
+# Is this installation the result of a crosscompile?
+if(NOT DEFINED CMAKE_CROSSCOMPILING)
+  set(CMAKE_CROSSCOMPILING "FALSE")
+endif()
+
+# Set default install directory permissions.
+if(NOT DEFINED CMAKE_OBJDUMP)
+  set(CMAKE_OBJDUMP "/usr/bin/objdump")
+endif()
+
+if(CMAKE_INSTALL_COMPONENT)
+  set(CMAKE_INSTALL_MANIFEST "install_manifest_${CMAKE_INSTALL_COMPONENT}.txt")
+else()
+  set(CMAKE_INSTALL_MANIFEST "install_manifest.txt")
+endif()
+
+string(REPLACE ";" "\n" CMAKE_INSTALL_MANIFEST_CONTENT
+       "${CMAKE_INSTALL_MANIFEST_FILES}")
+file(WRITE "/home/plex/Documents/code/c/c-basic/${CMAKE_INSTALL_MANIFEST}"
+     "${CMAKE_INSTALL_MANIFEST_CONTENT}")
diff --git a/compile-all.sh b/compile-all.sh
deleted file mode 100755
index 35b65a2..0000000
--- a/compile-all.sh
+++ /dev/null
@@ -1,24 +0,0 @@
-#!/bin/bash
-mkdir -p bin
-returnCode=0
-echo -e "compiling all files in working directory $(pwd)\n"
-for file in $(/bin/ls *.c); 
-do 
-    echo "compiling $file ..."
-    noext=$(echo "$file" | cut -f 1 -d '.')
-    gcc $file -o bin/$noext -lm
-    if [ "$?" -ne 0 ]
-    then
-        echo -e "\nERROR: could not compile $file !\n";
-        returnCode=1;
-    fi
-done
-echo -ne "\nfinished compiling all source files. ";
-if [ "$returnCode" -eq 0 ]
-then
-    echo -ne "No errors occured.";
-else
-    echo -ne "Some errors occured.";
-fi
-echo "";
-exit $returnCode
diff --git a/compile-and-run.sh b/compile-and-run.sh
deleted file mode 100755
index d7bd02a..0000000
--- a/compile-and-run.sh
+++ /dev/null
@@ -1,6 +0,0 @@
-#!/bin/bash
-mkdir -p bin
-noext=$(echo "$1" | cut -f 1 -d '.')
-echo "compiling $1 ..."
-gcc $1 -o bin/$noext -lm
-./bin/$noext $2 $3 $4 $5 $6 $7 $8 $9
diff --git a/compile.sh b/compile.sh
deleted file mode 100755
index 0405b59..0000000
--- a/compile.sh
+++ /dev/null
@@ -1,5 +0,0 @@
-#!/bin/bash
-mkdir -p bin
-echo "compiling $1 ..."
-noext=$(echo "$1" | cut -f 1 -d '.')
-gcc $1 -o bin/$noext -lm
diff --git a/complex.c b/complex.c
deleted file mode 100644
index dcd2a52..0000000
--- a/complex.c
+++ /dev/null
@@ -1,83 +0,0 @@
-#include <stdio.h>
-
-typedef struct
-{
-    float real;
-    float imaginary;
-}complex;
-
-complex assignComplex(){
-    float r, i;
-    scanf("%f", &r);
-    scanf("%f", &i);
-    complex c;
-    c.real = r;
-    c.imaginary = i;
-    return c;
-}
-
-void addComplex() {
-    printf("First complex\n");
-    complex a = assignComplex(); 
-    printf("Second complex\n");
-    complex b = assignComplex(); 
-
-    complex r;
-    r.real = a.real + b.real;
-    r.imaginary = a.imaginary + b.imaginary;
-    printf("Result: %f+%fi\n", r.real, r.imaginary);
-}
-
-void subComplex() {
-    printf("First complex\n");
-    complex a = assignComplex(); 
-    printf("Second complex\n");
-    complex b = assignComplex(); 
-
-    complex r;
-    r.real = a.real - b.real;
-    r.imaginary = a.imaginary - b.imaginary;
-    printf("Result: %f+%fi\n", r.real, r.imaginary);
-}
-
-void mulComplex() {
-    printf("First complex\n");
-    complex a = assignComplex(); 
-    printf("Second complex\n");
-    complex b = assignComplex(); 
-
-    complex r;
-    r.real = a.real * b.real;
-    r.imaginary = a.imaginary * b.imaginary;
-    printf("Result: %f+%fi\n", r.real, r.imaginary);
-}
-
-void divComplex() {
-    printf("First complex\n");
-    complex a = assignComplex(); 
-    printf("Second complex\n");
-    complex b = assignComplex(); 
-
-    complex r;
-    r.real = a.real / b.real;
-    r.imaginary = a.imaginary / b.imaginary;
-    printf("Result: %f+%fi\n", r.real, r.imaginary);
-}
-
-int main() {
-    printf("Usage:\n\toperations: + - * /\n\tquit: q\n");
-
-    char in;
-    while(1){
-
-        in = getchar();
-        switch(in){
-            case 'q': return 0;
-            case '+': addComplex(); break;
-            case '-': subComplex(); break;
-            case '*': mulComplex(); break;
-            case '/': divComplex(); break;
-            default: printf("kaputt\n"); break;
-        }
-    }
-}
diff --git a/dividableBy7.c b/dividableBy7.c
deleted file mode 100644
index bca2ea4..0000000
--- a/dividableBy7.c
+++ /dev/null
@@ -1,27 +0,0 @@
-/*
- * lower and upper end as user input
- * use a for loop to output all numbers for which 7|x is true.
- */
-
-#include <stdio.h>
-
-int main() {
-    
-    int a,b;
-    printf("input lower end:\n");
-    fflush(stdin);
-    scanf("%d",&a);
-    printf("input upper end:\n");
-    fflush(stdin);
-    scanf("%d",&b);
-
-    printf("inputs: %d %d\n", a, b);
-    for(int i=a; i<=b; i++){
-	if(i%7==0)
-	    printf("%d ", i);
-	if(i==b)
-	    printf("\n");
-    }
-    
-    return 0;
-}
diff --git a/dump.c b/dump.c
deleted file mode 100644
index d8cea6b..0000000
--- a/dump.c
+++ /dev/null
@@ -1,42 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-struct a {
-    int a;
-    char str[30];
-};
-
-/*
- * give an argument to keep the file /tmp/structdump
- * like this: bin/dump aaa
- */
-
-int main(int argc, char** argv){
-    struct a* mystruct = malloc(sizeof(struct a));
-    if(mystruct == NULL){
-        printf("malloc for 1st struct failed!\n");
-        return 1;
-    }
-    mystruct->a = 12;
-    char s[30] = "Wer das liest ist doof";
-    strcpy(mystruct->str, s);
-    FILE* fptr = fopen("/tmp/structdump", "wb");
-    fwrite(mystruct, sizeof(struct a), 1, fptr);
-    fclose(fptr);
-    free(mystruct);
-
-    fptr = fopen("/tmp/structdump", "rb"); 
-    mystruct = malloc(sizeof(struct a));
-    if(mystruct == NULL){
-        printf("malloc for 2nd struct failed!\n");
-        return 1;
-    }
-    fread(mystruct, sizeof(struct a), 1, fptr); 
-    printf("mystruct->a: %d\nmystruct->str: \"%s\"\n", mystruct->a, mystruct->str);   // SIGSEV
-    free(mystruct);
-    fclose(fptr);
-    if(argc<2)
-        remove("/tmp/structdump");
-    return 0;
-}
diff --git a/echo.c b/echo.c
deleted file mode 100644
index 8a35260..0000000
--- a/echo.c
+++ /dev/null
@@ -1,17 +0,0 @@
-#include <stdio.h>
-
-int main() {
-	char s[100];
-    //gets(s);
-    /*
-     * Never use gets().  Because it is impossible to tell without knowing the data in advance how many characters gets() will read,  and  be‐
-     * cause gets() will continue to store characters past the end of the buffer, it is extremely dangerous to use.  It has been used to break
-     * computer security.  Use fgets() instead.
-     *
-     * For more information, see CWE-242 (aka "Use of Inherently Dangerous Function") at http://cwe.mitre.org/data/definitions/242.html
-     *
-     */
-    fgets(s, sizeof(s), stdin);
-	printf("%s\n", s);
-	return 0;
-}
diff --git a/echochar.c b/echochar.c
deleted file mode 100644
index a2020a9..0000000
--- a/echochar.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <stdio.h>
-
-int main() {
-	
-	char a = getchar();
-	printf("%c", a);
-	return 0;
-}
diff --git a/euler.c b/euler.c
deleted file mode 100644
index 30272da..0000000
--- a/euler.c
+++ /dev/null
@@ -1,50 +0,0 @@
-#include <stdio.h>
-
-#include <stdio.h>
-#include <stdlib.h>
-
-// range of unsigned long long is:
-// 18.446.744.073.709.551.615
-// maximum factorial with this is 65!
-// Double goes up to 170!
-double factorial(double i) {
-
-   if(i <= 1) {
-      return 1;
-   }
-   return i * factorial(i - 1);
-}
-
- double factorialFor(double given){
-    double p = 1;
-
-    // someone said i need 2 for loops. Totally wrong?
-    for(int j=1;j<given;j++){
-        
-        p *= j;
-        //printf("[DEBUG]p is %f, j is %d\n", p, j);
-    }
-    return given * p;
-}
-
-double euler(int k) {
-    return 1/factorial(k);
-}
-int main(int argc, char *argv[]){
-    double res = 0, lres = 0;
-    int k = 0;
-    int end = 0;
-    while(!end){
-	res += euler(k);
-	printf("%f, %f\n", res, lres);
-	if(res==lres)
-	    end = 1;
-	else { 
-	    lres = res;
-	}
-	k++;
-    }
-    printf("calculated eulers number as %f\n", res);
-    return 0;
-}
-
diff --git a/factorial.c b/factorial.c
deleted file mode 100644
index cfe0366..0000000
--- a/factorial.c
+++ /dev/null
@@ -1,39 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-
-// range of unsigned long long is:
-// 18.446.744.073.709.551.615
-// maximum factorial with this is 65!
-// Double goes up to 170!
-double factorial(double i) {
-
-   if(i <= 1) {
-      return 1;
-   }
-   return i * factorial(i - 1);
-}
-
- double factorialFor(double given){
-    double p = 1;
-
-    // someone said i need 2 for loops. Totally wrong?
-    for(int j=1;j<given;j++){
-        
-        p *= j;
-        //printf("[DEBUG]p is %f, j is %d\n", p, j);
-    }
-    return given * p;
-}
-
-int main(int argc, char *argv[]){
-    if(argc<=1) {
-        printf("You did not feed me arguments, I will die now :( gimme ints");
-	return 1;
-    }  //otherwise continue on our merry way....
-
-    double num = atoi(argv[1]);
-    printf("the factorial of the given input calculated by a recursive algorithm is: %.0f\n", factorial(num));
-    printf("the factorial of the given input calculated by a nonrecursive algorithm is: %.0f\n", factorialFor(num));
-    return 0;
-}
-
diff --git a/fail.c b/fail.c
deleted file mode 100644
index 0630179..0000000
--- a/fail.c
+++ /dev/null
@@ -1,10 +0,0 @@
-#include <stdio.h>
-
-/*
- * This program has the purpose of returning a -1 value, indicating the shell that something has gone wrong
- * while the program was running.
- */
-
-int main(){
-    return -1;
-}
diff --git a/fread.c b/fread.c
deleted file mode 100644
index 15989c7..0000000
--- a/fread.c
+++ /dev/null
@@ -1,24 +0,0 @@
-#include <stdio.h>
-#include <string.h>
-
-int main () {
-   FILE *fp;
-   char c[] = "this is tutorialspoint";
-   char buffer[100];
-
-   /* Open file for both reading and writing */
-   fp = fopen("file.txt", "w+");
-
-   /* Write data to the file */
-   fwrite(c, strlen(c) + 1, 1, fp);
-
-   /* Seek to the beginning of the file */
-   fseek(fp, 0, SEEK_SET);
-
-   /* Read and display data */
-   fread(buffer, strlen(c)+1, 1, fp);
-   printf("%s\n", buffer);
-   fclose(fp);
-   
-   return(0);
-}
diff --git a/hello-world.c b/hello-world.c
deleted file mode 100644
index 04ce434..0000000
--- a/hello-world.c
+++ /dev/null
@@ -1,6 +0,0 @@
-#include <stdio.h>
-
-int main() {
-	printf("Hello world!\n");
-	return 0;
-}
diff --git a/options.c b/options.c
deleted file mode 100644
index 821e50a..0000000
--- a/options.c
+++ /dev/null
@@ -1,26 +0,0 @@
-#include <stdbool.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-
-int main(int argc, char *argv[])
-{
-    bool isCaseInsensitive = false;
-    int opt;
-    enum { CHARACTER_MODE, WORD_MODE, LINE_MODE } mode = CHARACTER_MODE;
-
-    while ((opt = getopt(argc, argv, "ilw")) != -1) {
-        switch (opt) {
-        case 'i': isCaseInsensitive = true; break;
-        case 'l': mode = LINE_MODE; break;
-        case 'w': mode = WORD_MODE; break;
-        default:
-            fprintf(stderr, "Usage: %s [-ilw] [file...]\n", argv[0]);
-            exit(EXIT_FAILURE);
-        }
-    }
-
-    // Now optind (declared extern int by <unistd.h>) is the index of the first non-option argument.
-    // If it is >= argc, there were no non-option arguments.
-
-}
diff --git a/pointer-arithmetic.c b/pointer-arithmetic.c
deleted file mode 100644
index 1c00204..0000000
--- a/pointer-arithmetic.c
+++ /dev/null
@@ -1,9 +0,0 @@
-#include <stdio.h>
-
-int main() {
-    int a[5] = {22, 33, 44, 55, 66};
-    int *ptr = NULL;
-    ptr = a;  /* point to the first array element */
-    for(int i = 0; i < 50; i++) {
-    printf(" value:0x%-10x\tor 0d%-16d\tAdress:%-8x\n", *(ptr+i), *(ptr+i), ptr+i);  /* 33 */
-}}
diff --git a/pointermagic.c b/pointermagic.c
deleted file mode 100644
index 0e9d93e..0000000
--- a/pointermagic.c
+++ /dev/null
@@ -1,19 +0,0 @@
-#include <stdio.h>
-
-void printLoc(int y) {
-    printf("Address of y is %x\n", &y);
-}
-
-void printPointerLoc(int *x) {
-    printf("Adress of x is %x\n", &x);
-    printf("Adress the x pointer points to is %x\n", x);
-    printf("Adress of whatever *x is is %x\n", *x);
-}
-
-int main() {
-    int a = 0xAAAA;
-    printf("Address of a is %x\n", &a);
-    printLoc(a);
-    printPointerLoc(&a);
-    return 0;
-}
diff --git a/primenumbers.c b/primenumbers.c
deleted file mode 100644
index 2fd7994..0000000
--- a/primenumbers.c
+++ /dev/null
@@ -1,43 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-
-int main(int argc, char** argv) {
-    int maxPrime = atoi(argv[1]);
-
-    int *arr1 = malloc(sizeof(int)*maxPrime);
-    if(arr1==NULL)
-        return -1;
-    for(int i=0; i<maxPrime; i++) {
-        arr1[i]=i+2;
-    }
-
-    int p = 2;
-
-    for(int i=1; i<maxPrime; i++) {
-        for(int j=1; j<maxPrime; j++) {
-            if((arr1[j]%p==0)&&(arr1[j]>0)&&(arr1[j]!=p))
-                arr1[j]=-1;
-        }
-        // get next prime in arr
-        // FIXME
-        p = arr1[i];
-        for(int l=0;l<512;l++){
-            if(p>0)
-                break;
-            else {
-                p = arr1[i+l]; 
-            }
-        }
-        for(int l=0;l<maxPrime;l++){
-        }
-    }
-    printf("\n");
-    printf("\n");
-    for(int i=0;i<maxPrime;i++){
-        if(arr1[i]>0)
-            printf("%d ", arr1[i]);
-    }
-    free(arr1);
-    printf("\n");
-    return 0;
-}
diff --git a/quersumme.c b/quersumme.c
deleted file mode 100644
index 7484927..0000000
--- a/quersumme.c
+++ /dev/null
@@ -1,30 +0,0 @@
-#include <stdio.h>
-int main() {
-    int a, digits = 0, b = 0;
-    printf("input a number for calculation\n");
-    fflush(stdin);
-    scanf("%d",&a);
-
-    int digit[128];
-
-    // look out for wrong order
-    for(int i=0; i<128; i++) {
-	digit[i] = a % 10;
-	if(a>0)
-	    a = a / 10;
-	else {
-	    if(digits==-1)
-		digits = i;
-	    digit[i] = -1;
-	}
-	//printf("%d. digit is: %d\n", i, digit[i]);
-    }
-
-    // array is in wrong order, but who cares for the quersumme
-    for(int i=0; i<128; i++){
-	if(digit[i]>0)
-	    b += digit[i];
-    }
-    printf("quersumme is: %d\n", b);
-    return 0;
-}
diff --git a/readfile.c b/readfile.c
deleted file mode 100644
index fb5f773..0000000
--- a/readfile.c
+++ /dev/null
@@ -1,23 +0,0 @@
-#include <stdlib.h>
-#include <stdio.h>
- 
-int main(void)
-{
-   char filename[] = "file.txt";
-   char buf[2];
-   FILE *fp;
-    
-   if ((fp = fopen(filename, "rb")) == NULL)
-   {
-      printf("Unable to open file: %s\n", filename);
-      return EXIT_FAILURE;
-   }
-    
-   if (fread(buf, 1, 2, fp) == 2)
-   {
-      printf("%02x %02x\n", (int) buf[0], (int) buf[1]);
-   }
-    
-   fclose(fp);
-   return 0;
-}
diff --git a/redefinition-if.c b/redefinition-if.c
deleted file mode 100644
index 8c03c48..0000000
--- a/redefinition-if.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <stdio.h>
-int main() {
-    int a;
-    if(1){
-	int a;	// works, this a is only in scope of the if statement.
-    }
-    return 0;
-}
diff --git a/redefinition.c b/redefinition.c
deleted file mode 100644
index 081dcea..0000000
--- a/redefinition.c
+++ /dev/null
@@ -1,7 +0,0 @@
-#include <stdio.h>
-int a = 1;
-int main() {
-    int a = 2;
-    printf("%d\n", a); // local overrides global
-    return 0;
-}
diff --git a/return-specified.c b/return-specified.c
deleted file mode 100644
index 7477ffa..0000000
--- a/return-specified.c
+++ /dev/null
@@ -1,15 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-
-/*
- * This program takes the given argument and returns it as an integer.
- * It might be useful to test a shell.
- */
-
-int main(int argc, char** argv){
-    if(argc<2){
-        printf("No argument given.\n");
-        return -1;
-    }
-    return atoi(argv[1]);
-}
diff --git a/scanf-test.c b/scanf-test.c
deleted file mode 100644
index 8a489b8..0000000
--- a/scanf-test.c
+++ /dev/null
@@ -1,11 +0,0 @@
-#include <stdio.h>
-
-int main() {
-    int a;
-    float f;
-    char s[20];
-    printf("input an integer, a float, then a string.\n");
-    scanf("%d %f %s", &a, &f, s);
-    printf("%d %f %s\n", a, f, s);
-    return 0;
-}
diff --git a/scnaf-hex-test.c b/scnaf-hex-test.c
deleted file mode 100644
index b9b7fa2..0000000
--- a/scnaf-hex-test.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <stdio.h>
-
-int main() {
-    int a;
-    scanf("%x", &a);
-    printf("hex: %x dec: %d\n", a, a);
-    return 0;
-    }
diff --git a/signed-to-unsigned.c b/signed-to-unsigned.c
deleted file mode 100644
index 9f461a7..0000000
--- a/signed-to-unsigned.c
+++ /dev/null
@@ -1,6 +0,0 @@
-#include <stdio.h>
-
-int main() {
-    signed int a = -1;
-    printf("%u\n",a); // no need to type cast. %u interprets given bytes of type unsigned int regardless of the datatype. truly low level
-    }
diff --git a/sizeofs.c b/sizeofs.c
deleted file mode 100644
index 4a33c01..0000000
--- a/sizeofs.c
+++ /dev/null
@@ -1,10 +0,0 @@
-#include <stdio.h>
-
-int main() {
-    printf("int: %ld \n", sizeof(int));
-    printf("float: %ld \n", sizeof(float));
-    printf("double: %ld \n", sizeof(double));
-    printf("char: %ld \n", sizeof(char));
-
-    return 0;
-}
diff --git a/success.c b/success.c
deleted file mode 100644
index 4278030..0000000
--- a/success.c
+++ /dev/null
@@ -1,10 +0,0 @@
-#include <stdio.h>
-
-/*
- * This program has the purpose of returning a 0 value, indicating to the shell that the program was
- * executed successfully.
- */
-
-int main(){
-    return 0;
-}
diff --git a/sum.c b/sum.c
deleted file mode 100644
index 75126f5..0000000
--- a/sum.c
+++ /dev/null
@@ -1,11 +0,0 @@
-#include <stdio.h>
-
-int main(){
-
-    int result = 0;
-    for (int i = 1; i < 101; i++){
-	result+=i;
-    }
-    printf("sum of 1 up to 100 is: %d\n", result);
-    return 0;
-}
diff --git a/tabtest.c b/tabtest.c
deleted file mode 100644
index 7902237..0000000
--- a/tabtest.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <stdio.h>
-
-int main() {
-    printf("horizontal\ttab\n");
-    printf("vertical%ctab\n", 11);
-    printf("reference line\n");
-    return 0;
-}
diff --git a/umlaut.c b/umlaut.c
deleted file mode 100644
index bbdb9d3..0000000
--- a/umlaut.c
+++ /dev/null
@@ -1,3 +0,0 @@
-#include <stdio.h>
-int main() { return 0; }
-int zähler() { return 0; } // umlaute is an unknown char for gcc
diff --git a/unary-double-not.c b/unary-double-not.c
deleted file mode 100644
index a611f37..0000000
--- a/unary-double-not.c
+++ /dev/null
@@ -1,6 +0,0 @@
-#include <stdio.h>
-
-int main(){
-    printf("%d\n",!!42);
-    return 0;
-}
diff --git a/warning.c b/warning.c
deleted file mode 100644
index 06373c6..0000000
--- a/warning.c
+++ /dev/null
@@ -1,15 +0,0 @@
-#include <stdio.h>
-
-int main(){
-    char s[2];
-    /*
-     * The following line of code is unsafe. It writes up to 10 bytes into the char array 's', which is only
-     * 2 Bytes big. A Buffer Overflow can happen. I have chosen to keep that line, because i wanted a source
-     * file that produces a compiler warning when it is compiled. That is the true purpose of this file.
-     *
-     * a safe alternative would be: fgets(s, 2, stdin);
-     */
-    fgets(s, 10, stdin);    // UNSAFE 
-    printf("%s\n",s);
-    return 0;
-}